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Normal and Abnormal Labor

Labor is the normal physiologic process defined as uterine contractions resulting in dilatation and effacement of the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy, which culminates in expulsion of the fetus and the products of conception. Labor has 3 stages: the 1st stage starts with the onset of regular Regular Insulin contractions, the 2nd stage starts with full cervical dilation, and the 3rd stage starts immediately after fetal delivery and ends with delivery of the placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity. The primary factors required for labor to progress normally are the three Ps PS Invasive Mechanical Ventilation: power (uterine contractions), passenger (the fetus), and passage (the maternal pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy). Labor may become abnormally protracted and require augmentation, usually with oxytocin, to prevent maternal and fetal complications.

Last updated: Jul 14, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Overview

Definition: Normal labor

Labor is defined as regular Regular Insulin uterine contractions that cause cervical dilation and effacement, leading to delivery of the fetus and the products of conception. Characteristics of normal labor include:

  • Gestational age Gestational age The age of the conceptus, beginning from the time of fertilization. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last menstruation which is about 2 weeks before ovulation and fertilization. Pregnancy: Diagnosis, Physiology, and Care: occurs at 37–42 weeks of gestational age Gestational age The age of the conceptus, beginning from the time of fertilization. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last menstruation which is about 2 weeks before ovulation and fertilization. Pregnancy: Diagnosis, Physiology, and Care (full-term)
  • Onset: spontaneous (as opposed to induced)
  • Progression: spontaneous, without complications 

There are subtle differences in normal labor between primiparous and multiparous women (reviewed below).

  • Primiparous: a woman’s 1st delivery
  • Multiparous: a woman with prior deliveries

Monitoring progress of labor

Labor progress is followed by serial cervical exams to assess dilation, effacement, and fetal station.

  • Cervical dilation: 
  • Cervical effacement:
    • An estimate of cervical thinning
    • Cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy starts at > 2 cm → effaces to paper thin (full effacement)
    • Reported as a percentage of progress
    • Full effacement: 100% effaced 
  • Fetal station:
    • How high (or low) the presenting fetal part is compared to the maternal ischial spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy
    • Reported in centimeters:
      • Positive numbers denote a lower fetal station, closer to the vaginal introitus
      • Negative numbers denote a fetal station higher in the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy
    • Fetal head at the introitus: +3–5 cm
Cervical changes during the first stage of labor

Cervical changes during the first stage of labor:
At the onset of the labor, the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy is usually undilated. The first stage ends when the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy is fully dilated (10 cm).

Image: “2920 Stages of Childbirth-02” by OpenStax College. License: CC BY 4.0, cropped by Lecturio.

Stages of labor

There are 3 stages of labor:

  1. The 1st stage: 
    • Begins with the onset of regular Regular Insulin uterine contractions that cause cervical change
    • Ends with full cervical dilation (10 cm)
  2. The 2nd stage: 
    • Begins when the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy reaches full dilation (10 cm)
    • Ends with delivery of the fetus
  3. The 3rd stage: 
    • Begins immediately after delivery of the fetus 
    • Ends with delivery of the placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity
Progression through the 3 stages of labor

Progression through the 3 stages of labor

Image by Lecturio.

Related videos

The 3 Ps: Power, Passenger, and Passage

For labor to progress normally, there needs to be adequate power from uterine contractions, the fetus needs to tolerate the contractions, and the fetus needs to fit through the maternal pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy. These requirements are referred to as the 3 Ps PS Invasive Mechanical Ventilation: Power, Passenger, and Passage.

Power: Uterine contractions

  • Contractions must be powerful enough to dilate the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy and expel the fetus
  • Can be measured by:
    • External pressure transducer Transducer A device placed on the patient’s body to visualize a target Ultrasound (Sonography) (tocometry): measures frequency and strength of contractions relative to each other
    • Internal uterine pressure catheter (IUPC): measures frequency and numerical strength of contractions in Montevideo units (MVUs)
  • Montevideo units: the strength of all contractions are summated within a 10-minute period:
    • “Adequate power” to effect delivery: ≥ 200 MVUs in 10 minutes
    • “Inadequate power” is a cause of abnormal labor progress.

Passenger: Fetus

Multiple characteristics of the fetus are required in order to safely deliver vaginally. The fetal head must ultimately be flexed and directly aligned with the maternal spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy in order to fit through the maternal pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy.

  • Presentation: based on the “presenting part” of the fetus at the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy:
    • Vertex: head down
    • Breech: 
      • Frank breech: bottom down, legs extended
      • Complete breech: bottom down, legs flexed
      • Footling breech: feet down
    • Face: 
      • Mentum anterior (MA): chin Chin The anatomical frontal portion of the mandible, also known as the mentum, that contains the line of fusion of the two separate halves of the mandible (symphysis menti). This line of fusion divides inferiorly to enclose a triangular area called the mental protuberance. On each side, inferior to the second premolar tooth, is the mental foramen for the passage of blood vessels and a nerve. Melasma is anterior, face can flex → compatible with vaginal delivery
      • Mentum posterior (MP): chin Chin The anatomical frontal portion of the mandible, also known as the mentum, that contains the line of fusion of the two separate halves of the mandible (symphysis menti). This line of fusion divides inferiorly to enclose a triangular area called the mental protuberance. On each side, inferior to the second premolar tooth, is the mental foramen for the passage of blood vessels and a nerve. Melasma is posterior, face cannot flex, incompatible with vaginal delivery
      • Remember: “MA can, PA can’t” for vaginal deliveries
    • Brow: forehead Forehead The part of the face above the eyes. Melasma down, large diameter, incompatible with vaginal delivery
  • Positions: orientation Orientation Awareness of oneself in relation to time, place and person. Psychiatric Assessment of the fetal head in relation to the maternal pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy in vertex presentations:
    • Occiput anterior ( OA OA Osteoarthritis (OA) is the most common form of arthritis, and is due to cartilage destruction and changes of the subchondral bone. The risk of developing this disorder increases with age, obesity, and repetitive joint use or trauma. Patients develop gradual joint pain, stiffness lasting < 30 minutes, and decreased range of motion. Osteoarthritis): fetus is facing maternal spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy; easiest for delivery
    • Occiput posterior (OP): fetus is facing maternal bladder Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination. Pyelonephritis and Perinephric Abscess; more challenging
    • Occiput transverse (OT): fetal head is sideways (facing a maternal hip)
  • Fetal tolerance Tolerance Pharmacokinetics and Pharmacodynamics of labor: infant must tolerate the relative ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage that occurs during uterine contractions without becoming acidotic
  • Normal size infant: infant must fit through maternal pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy
  • Number of infants: 
    • Singletons and twins are candidates for a trial of labor
    • Surviving triplets and higher-order multiples should be delivered via cesarean 
Diameters of the fetal head

Diameters of the fetal head:
Vertex presentation: suboccipitobregmatic diameter of approximately 9.5 cm
Vertex presentation with deflexed head: occipitofrontal diameter of approximately 11.5 cm
Brow presentation: supraoccipitomental diameter of approximately 13 cm
Face presentation: submentobregmatic diameter of approximately 9.5 cm

Image by Lecturio. License: CC BY-NC-SA 4.0

Passage: Pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy

The maternal pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy must be large enough to accommodate the fetus. The pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy is assessed as “adequate” or “inadequate” for a trial of labor on the initial exam.

  • Pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy shapes: classified based on the shape of the pelvic inlet Pelvic inlet Pelvis: Anatomy:
    • Gynecoid: round and most spacious → most easily allows the fetal head to rotate to OA OA Osteoarthritis (OA) is the most common form of arthritis, and is due to cartilage destruction and changes of the subchondral bone. The risk of developing this disorder increases with age, obesity, and repetitive joint use or trauma. Patients develop gradual joint pain, stiffness lasting < 30 minutes, and decreased range of motion. Osteoarthritis
    • Anthropoid: longer anteroposterior diameter and narrow → more commonly causes the head to rotate to OP
    • Platypelloid: wider and narrow → more commonly causes the head to stay OT
    • Android: heart shaped → fetal head may have difficulty engaging
  • Clinical relevance of pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy shape:
    • Difficult to determine on exam
    • No shape is a contraindication for a trial of labor.
    • Gynecoid is the easiest for vaginal delivery
    • Android and platypelloid are the most difficult for vaginal delivery
    • May contribute to abnormal labor patterns

The 1st Stage of Labor

Definitions

  • Starts with the onset of regular Regular Insulin contractions that result in:
    • Cervical change (dilation and effacement)
    • Descent of the fetus
  • Ends with full cervical dilation (10 cm) 
  • Divided into latent and active phases
Divisions and timing of the first stage of labor

Divisions and typical timing of the 1st stage of labor:
Accel.: acceleration
Decel.: deceleration Deceleration A decrease in the rate of speed. Blunt Chest Trauma
Max: maximum

Image by Lecturio.

Latent phase

In the late 3rd trimester, irregular contractions and runs of nonpersistent regular Regular Insulin contractions are common. The latent phase is the establishment of true labor, with regular Regular Insulin persistent contractions that will continue through delivery.

  • Dilation: 0 to 4–6 cm 
  • Effacement: variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables
    • Primiparous: cervical effacement usually occurs before significant dilation
    • Multiparous: dilation usually precedes significant effacement 
  • Station: high (< 0)
  • Contractions: 
    • Frequency: regular Regular Insulin, ≥ 3 per 10 minutes
    • Intensity: mild to moderate
    • Anesthesia Anesthesia A state characterized by loss of feeling or sensation. This depression of nerve function is usually the result of pharmacologic action and is induced to allow performance of surgery or other painful procedures. Anesthesiology: History and Basic Concepts is generally not required.
  • Typical duration: 
    • Primiparous: < 20 hours
    • Multiparous: < 14 hours

Active phase

The active phase is a time of more rapid cervical change leading up to delivery.

  • Dilation: 6–10 cm 
    • Primiparous: 1.2 cm/hour
    • Multiparous: 1.5 cm/hour
  • Effacement: continues to 100%
  • Station: progressive descent to at least the ischial spines (0 station)
  • Contractions: 
    • Frequency: regular Regular Insulin, ≥ 3 per 10 minutes
    • Intensity: strong
    • Anesthesia Anesthesia A state characterized by loss of feeling or sensation. This depression of nerve function is usually the result of pharmacologic action and is induced to allow performance of surgery or other painful procedures. Anesthesiology: History and Basic Concepts is often requested.
Table: Length of the 1st stage of labor
Primiparous Multiparous
Latent labor Lasts < 20 hours Lasts < 14 hours
Active labor 1.2 cm/hour 1.5 cm/hour
Latent phase: onset of contractions until 4–6 cm cervical dilation
Active phase: begins at 4‒6 cm dilation and lasts until the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy is fully dilated at 10 cm

Labor management

General management:

  • Continuous care and emotional support to the mother
  • Ambulation in low-risk women 
  • Adequate hydration

Maternal assessment:

  • Labor progression: serial cervical exams
  • Contraction adequacy: Assess strength and frequency via palpation Palpation Application of fingers with light pressure to the surface of the body to determine consistency of parts beneath in physical diagnosis; includes palpation for determining the outlines of organs. Dermatologic Examination and/or monitoring.
  • Vital signs
  • Urine output

Fetal assessment:

  • Intermittent auscultation of the fetal heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology (lowest-risk women only)
  • Continuous cardiotocography (majority of women)
    • Includes women with any medical pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways management
    • Includes most women with any medical or obstetric complications

Abnormalities in the 1st stage of labor

Table: Diagnosis and management of abnormalities in the 1st stage of labor
Diagnosis Criteria Management
Protracted latent phase Abnormally long duration of the latent phase:
  • Primiparous: > 20 hours
  • Multiparous: > 14 hours
Options include:
Protracted active phase
  • Cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy is ≥ 6 cm and
  • Dilating < 1 cm over 2 hours
  • Oxytocin
  • Amniotomy (if membranes are not already ruptured)
Active phase arrest Cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy is ≥ 6 cm and:
  • No cervical change for ≥ 4 hours despite adequate contractions
    or
  • No cervical change for ≥ 6 hours regardless of contraction adequacy
Cesarean delivery Cesarean Delivery Cesarean delivery (CD) is the operative delivery of ≥ 1 infants through a surgical incision in the maternal abdomen and uterus. Cesarean deliveries may be indicated for a number of either maternal or fetal reasons, most commonly including fetal intolerance to labor, arrest of labor, a history of prior uterine surgery, fetal malpresentation, and placental abnormalities. Cesarean Delivery (CD)
Table: Etiologies and management of abnormalities in the first stage of labor
Etiology Management
Power Inadequate power: < 200 MVUs measured with an IUPC Pitocin: to ↑ contraction strength

Passenger
Abnormal presentation:
  • Breech
  • Face
  • Brow
  • Cesarean delivery Cesarean Delivery Cesarean delivery (CD) is the operative delivery of ≥ 1 infants through a surgical incision in the maternal abdomen and uterus. Cesarean deliveries may be indicated for a number of either maternal or fetal reasons, most commonly including fetal intolerance to labor, arrest of labor, a history of prior uterine surgery, fetal malpresentation, and placental abnormalities. Cesarean Delivery recommended for:
    • Breech
    • Brow
    • Face: mentum posterior
  • Observation:
    • Face: mentum anterior
Abnormal position:
  • Occiput posterior
  • Occiput transverse
  • Observation
  • Attempt manual rotation Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. X-rays
Fetal intolerance to labor / fetal heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology abnormalities Fetal resuscitation Resuscitation The restoration to life or consciousness of one apparently dead. . Neonatal Respiratory Distress Syndrome:
  • Reposition the mother
  • Maternal oxygen
  • Maternal IV fluid bolus
  • ↓ pitocin
  • Amnioinfusion Amnioinfusion Oligohydramnios: an intrauterine fluid bolus delivered through an IUPC catheter
Higher order multifetal gestations Cesarean delivery Cesarean Delivery Cesarean delivery (CD) is the operative delivery of ≥ 1 infants through a surgical incision in the maternal abdomen and uterus. Cesarean deliveries may be indicated for a number of either maternal or fetal reasons, most commonly including fetal intolerance to labor, arrest of labor, a history of prior uterine surgery, fetal malpresentation, and placental abnormalities. Cesarean Delivery
Pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy Cephalopelvic disproportion: fetal head does not fit through the maternal pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy Cesarean delivery Cesarean Delivery Cesarean delivery (CD) is the operative delivery of ≥ 1 infants through a surgical incision in the maternal abdomen and uterus. Cesarean deliveries may be indicated for a number of either maternal or fetal reasons, most commonly including fetal intolerance to labor, arrest of labor, a history of prior uterine surgery, fetal malpresentation, and placental abnormalities. Cesarean Delivery
MVU: Montevideo unit
IUPC: Internal uterine pressure catheter

The 2nd Stage of Labor

The 2nd stage of labor begins with complete dilatation of the cervix Cervix The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Externally, the cervix is lined by stratified squamous cells; however, the cervical canal is lined by columnar epithelium. Uterus, Cervix, and Fallopian Tubes: Anatomy and ends with delivery of the infant.

The cardinal movements of labor

The cardinal movements of labor describe the movements a fetus goes through as it moves through the maternal pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy. These movements align the largest parts of the infant with the largest diameter through the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy (the anteroposterior diameter between the pubic bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types and the sacrum Sacrum Five fused vertebrae forming a triangle-shaped structure at the back of the pelvis. It articulates superiorly with the lumbar vertebrae, inferiorly with the coccyx, and anteriorly with the ilium of the pelvis. The sacrum strengthens and stabilizes the pelvis. Vertebral Column: Anatomy).

  • Engagement: occurs in the 1st stage 
    • Passage of the fetal head into the pelvic inlet Pelvic inlet Pelvis: Anatomy
    • Fetal head is in an OT position: looking sideways, with the fetal head aligned with the fetal spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy
  • Descent: downward passage of the fetal head through the pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy
  • Flexion Flexion Examination of the Upper Limbs
    • Passive flexion Flexion Examination of the Upper Limbs of the fetal head (fetal chin Chin The anatomical frontal portion of the mandible, also known as the mentum, that contains the line of fusion of the two separate halves of the mandible (symphysis menti). This line of fusion divides inferiorly to enclose a triangular area called the mental protuberance. On each side, inferior to the second premolar tooth, is the mental foramen for the passage of blood vessels and a nerve. Melasma touches the fetal chest) as the head is pushed against maternal bony structures
    • Allows the narrowest diameter of the head to present
  • Internal rotation Internal Rotation Examination of the Upper Limbs
    • Rotation Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. X-rays of the fetal head to an anteroposterior direction
    • This rotation Rotation Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. X-rays turns the fetal head relative to its own spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy
      • Example: The fetal head is now looking down, while the fetal body is still mostly facing to the side.
      • This prepares the fetal head to move under the pubic bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types in the next step
  • Extension Extension Examination of the Upper Limbs: fetal head extends ( chin Chin The anatomical frontal portion of the mandible, also known as the mentum, that contains the line of fusion of the two separate halves of the mandible (symphysis menti). This line of fusion divides inferiorly to enclose a triangular area called the mental protuberance. On each side, inferior to the second premolar tooth, is the mental foramen for the passage of blood vessels and a nerve. Melasma lifts off the chest) as it moves under the pubic bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types and appears through the vaginal opening
  • External rotation External Rotation Examination of the Upper Limbs/restitution: 
    • Head rotates back to transverse to align with the fetal spine Spine The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column: Anatomy again.
    • Allows delivery of the shoulders beneath the pubic bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types
  • Expulsion: 
    • Delivery of the rest of the fetal body, which has a smaller diameter than the fetal head and shoulders
    • Usually rapid
The cardinal movements of labor

The cardinal movements of labor

Image by Lecturio.

Normal parameters

  • Evaluated with the descent of the fetal head (station).
  • Normal duration of the 2nd stage depends on:
    • Primiparous versus multiparous
    • Epidural versus no epidural
  • Infant should be making continuous downward progress throughout the 2nd stage.
Table: Normal parameters for the 2nd stage of labor
Primiparous Multiparous
With an epidural 3 hours 2 hours
Without an epidural 2 hours 1 hour

Management

  • Continue to monitor mother and infant as in the 1st stage of labor, but more frequently for:
    • Vital signs
    • Urine output
    • Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways control
    • Fetal heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology (FHR) and uterine contractions:
      • Cardiotocography (FHR tracing), or
      • Intermittent auscultation with palpation Palpation Application of fingers with light pressure to the surface of the body to determine consistency of parts beneath in physical diagnosis; includes palpation for determining the outlines of organs. Dermatologic Examination of contractions
  • Discourage lying flat → woman should have a hip roll under 1 side to keep the baby off the inferior vena cava Inferior vena cava The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy
  • Push/bear down with each contraction
Table: Abnormalities and management in 2nd stage of labor
Abnormality Definition Management
Protracted 2nd stage Duration is outside normal parameters
  • Observation: considered if fetal and maternal status are reassuring
  • Operative vaginal delivery Operative Vaginal Delivery Operative vaginal delivery is the use of obstetric forceps or a vacuum extractor to effect delivery of a fetus. Complications during Childbirth if ≥ +2 station
  • Cesarean delivery Cesarean Delivery Cesarean delivery (CD) is the operative delivery of ≥ 1 infants through a surgical incision in the maternal abdomen and uterus. Cesarean deliveries may be indicated for a number of either maternal or fetal reasons, most commonly including fetal intolerance to labor, arrest of labor, a history of prior uterine surgery, fetal malpresentation, and placental abnormalities. Cesarean Delivery if < +2 station
Arrested 2nd stage No descent for ≥ 2 hours Cesarean delivery Cesarean Delivery Cesarean delivery (CD) is the operative delivery of ≥ 1 infants through a surgical incision in the maternal abdomen and uterus. Cesarean deliveries may be indicated for a number of either maternal or fetal reasons, most commonly including fetal intolerance to labor, arrest of labor, a history of prior uterine surgery, fetal malpresentation, and placental abnormalities. Cesarean Delivery
Shoulder dystocia Shoulder Dystocia Obstetric complication during obstetric delivery in which exit of the fetus is delayed due to physical obstruction involving fetal shoulder(s). Complications during Childbirth Fetal head delivers, but shoulder remains lodged under the pubic bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types → obstetric emergency: fetus not getting oxygen during this time
  • Flex maternal legs
  • Suprapubic pressure: attempting to dislodge the anterior fetal shoulder
  • Delivery of the posterior arm Arm The arm, or “upper arm” in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm: Anatomy
  • Rotational maneuvers: attempt to rotate the fetal shoulder to allow delivery
  • Additional advanced maneuvers of last resort

The 3rd Stage of Labor

The 3rd stage of labor starts immediately after delivery of the baby and ends with complete expulsion of the placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity.

Clinical presentation

Signs that the placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity is ready to deliver include:

  • Lengthening of the umbilical cord Umbilical cord The flexible rope-like structure that connects a developing fetus to the placenta in mammals. The cord contains blood vessels which carry oxygen and nutrients from the mother to the fetus and waste products away from the fetus. Placenta, Umbilical Cord, and Amniotic Cavity
  • Gush of blood
  • Uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy becomes hard and globular

Management

  • Active management:
    • Gentle downward traction on the umbilical cord Umbilical cord The flexible rope-like structure that connects a developing fetus to the placenta in mammals. The cord contains blood vessels which carry oxygen and nutrients from the mother to the fetus and waste products away from the fetus. Placenta, Umbilical Cord, and Amniotic Cavity with countertraction on the uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Uterus, Cervix, and Fallopian Tubes: Anatomy (to avoid uterine inversion)
    • IM or IV injection of oxytocin
  • Passive management:
    • Observation until spontaneous placental delivery occurs
    • Associated with higher rates of postpartum hemorrhage Postpartum hemorrhage Postpartum hemorrhage is one of the most common and deadly obstetric complications. Since 2017, postpartum hemorrhage has been defined as blood loss greater than 1,000 mL for both cesarean and vaginal deliveries, or excessive blood loss with signs of hemodynamic instability. Postpartum Hemorrhage
  • Normal parameters:
    • < 30 minutes
    • Typically takes 5–10 minutes 

Prolonged 3rd stage of labor

  • Diagnosis: 3rd stage > 30 minutes
  • Etiology: 
    • Abnormal placentation (e.g., placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity accreta)
    • Separated but trapped placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity due to rapid contraction of the lower uterine segment
  • Management:
    • Manual uterine exploration
    • Uterine relaxants (if lower uterine segment is preventing expulsion)
    • Surgical exploration
Human placenta shown a few minutes after birth

Human placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity shown a few minutes after birth:
The side shown faces the baby with the umbilical cord Umbilical cord The flexible rope-like structure that connects a developing fetus to the placenta in mammals. The cord contains blood vessels which carry oxygen and nutrients from the mother to the fetus and waste products away from the fetus. Placenta, Umbilical Cord, and Amniotic Cavity top right. The unseen side connects to the uterine wall.

Image: “Human placenta Placenta A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (chorionic villi) derived from trophoblasts and a maternal portion (decidua) derived from the uterine endometrium. The placenta produces an array of steroid, protein and peptide hormones (placental hormones). Placenta, Umbilical Cord, and Amniotic Cavity baby side” by Habj. License: Public Domain

Clinical Relevance

  • False labor (also known as Braxton-Hicks contractions Braxton-Hicks contractions Irregular contractions that do not cause cervical change and become more noticeable as the pregnancy progresses Pregnancy: Diagnosis, Physiology, and Care): irregular uterine contractions or runs of regular Regular Insulin contractions without cervical changes. These contractions do not increase in intensity or duration, and they are common and normal in the 3rd trimester. Women should be reassured and counseled about hydration, as dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration was found to be associated with false labor.
  • Prelabor rupture of membrane: the rupture of membranes ( chorion Chorion The outermost extraembryonic membrane surrounding the developing embryo. In reptiles and birds, it adheres to the shell and allows exchange of gases between the egg and its environment. In mammals, the chorion evolves into the fetal contribution of the placenta. Placenta, Umbilical Cord, and Amniotic Cavity and amnion Amnion The innermost membranous sac that surrounds and protects the developing embryo which is bathed in the amniotic fluid. Amnion cells are secretory epithelial cells and contribute to the amniotic fluid. Placenta, Umbilical Cord, and Amniotic Cavity) before the onset of labor. Women usually present with a “gush of amniotic fluid Amniotic fluid A clear, yellowish liquid that envelopes the fetus inside the sac of amnion. In the first trimester, it is likely a transudate of maternal or fetal plasma. In the second trimester, amniotic fluid derives primarily from fetal lung and kidney. Cells or substances in this fluid can be removed for prenatal diagnostic tests (amniocentesis). Placenta, Umbilical Cord, and Amniotic Cavity” from the vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor: Anatomy followed by a continuous dribble. Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease frequently develop after the membranes have been ruptured for a prolonged period (> 18 hours). Sterile Sterile Basic Procedures speculum examination Speculum Examination Diagnostic Procedures in Gynecology is done to visualize the presence of amniotic fluid Amniotic fluid A clear, yellowish liquid that envelopes the fetus inside the sac of amnion. In the first trimester, it is likely a transudate of maternal or fetal plasma. In the second trimester, amniotic fluid derives primarily from fetal lung and kidney. Cells or substances in this fluid can be removed for prenatal diagnostic tests (amniocentesis). Placenta, Umbilical Cord, and Amniotic Cavity pooling within the posterior vaginal fornix Fornix Vagina, Vulva, and Pelvic Floor: Anatomy. Prelabor rupture of membrane may precipitate labor, but it is not considered to be labor in and of itself.

References

  1. Ehsanipoor, R.M., Satin, A. (2020). Normal and abnormal labor progression. UpToDate. Retrieved March 18, 2021, from https://www.uptodate.com/contents/normal-and-abnormal-labor-progression
  2.  American College of Obstetricians and Gynecologists Committee on Obstetrics (2019). Approaches to limit intervention during labor and birth. Committee opinion 766. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2019/02/approaches-to-limit-intervention-during-labor-and-birth 
  3. American College of Obstetricians and Gynecologists Obstetric Care Consensus No. 1. (2014). Safe prevention of the primary cesarean delivery. Retrieved Feb 10, 2022 from https://www.acog.org/clinical/clinical-guidance/obstetric-care-consensus/articles/2014/03/safe-prevention-of-the-primary-cesarean-delivery
  4. Ehsanipoor, R.M., Satin, A. (2021). Labor: Diagnosis and management of an abnormal first stage. UpToDate. Retrieved Feb 10, 2022 from https://www.uptodate.com/contents/labor-diagnosis-and-management-of-an-abnormal-first-stage
  5. Ehsanipoor, R.M., Satin, A. (2021). Labor: Diagnosis and management of a prolonged second stage. UpToDate. Retrieved Feb 10, 2022 from https://www.uptodate.com/contents/labor-diagnosis-and-management-of-a-prolonged-second-stage

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