Spontaneous Abortion

Spontaneous abortion, also known as miscarriage, is the loss of a pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care before 20 weeks' gestation. However, the layperson use of the term “abortion” is often intended to refer to induced termination of a pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care, whereas “miscarriage” is preferred for spontaneous loss. Most spontaneous abortions occur within the 1st 12 weeks of gestation and can be caused by several factors such as infection, trauma, and genetic and autoimmune causes. There are different types of spontaneous abortions, including threatened, inevitable, incomplete, complete, and missed abortions. Spontaneous abortions are diagnosed based on history, physical examination, and ultrasound findings. Management options include expectant, medical, or surgical therapy.

Last updated: Sep 29, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Overview

Definition

Spontaneous abortion is the noninduced loss of pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care before 20 weeks’ gestation.

Epidemiology

  • Common complication of early pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care
  • Accounts for pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care loss in 10%–20% of clinically recognized pregnancies
  • Occurs in all age groups, but the incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency is higher in women > 35 years of age
  • There is conflicting data on racial predilection.

Classification

Spontaneous abortion can be classified into the following types (see “Clinical Presentation and Diagnosis” for details):

  • Threatened abortion
  • Inevitable abortion
  • Incomplete abortion
  • Complete abortion
  • Missed abortion

Etiology

There are many potential causes for spontaneous abortion.

Maternal factors

  • Advanced maternal age (> 35 years)
  • Medical conditions:
    • Antiphospholipid syndrome Antiphospholipid syndrome Antiphospholipid syndrome (APLS) is an acquired autoimmune disorder characterized by the persistent presence of antiphospholipid antibodies, which create a hypercoagulable state. These antibodies are most commonly discovered during a workup for a thrombotic event or recurrent pregnancy loss, which are the 2 most common clinical manifestations. Antiphospholipid Syndrome
    • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
    • Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus
    • Obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity
    • Hyperthyroidism Hyperthyroidism Hypersecretion of thyroid hormones from the thyroid gland. Elevated levels of thyroid hormones increase basal metabolic rate. Thyrotoxicosis and Hyperthyroidism
    • Coagulopathies Coagulopathies Hemothorax
    • Autoimmune conditions
  • 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:
    • Cytomegalovirus Cytomegalovirus CMV is a ubiquitous double-stranded DNA virus belonging to the Herpesviridae family. CMV infections can be transmitted in bodily fluids, such as blood, saliva, urine, semen, and breast milk. The initial infection is usually asymptomatic in the immunocompetent host, or it can present with symptoms of mononucleosis. Cytomegalovirus
    • Parvovirus B19 Parvovirus B19 Primate erythroparvovirus 1 (generally referred to as parvovirus B19, B19 virus, or sometimes erythrovirus B19) ranks among the smallest DNA viruses. Parvovirus B19 is of the family Parvoviridae and genus Erythrovirus. In immunocompetent humans, parvovirus B19 classically results in erythema infectiosum (5th disease) or “slapped cheek syndrome.” Parvovirus B19
    • Toxoplasmosis Toxoplasmosis Toxoplasmosis is an infectious disease caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. Felines are the definitive host, but transmission to humans can occur through contact with cat feces or the consumption of contaminated foods. The clinical presentation and complications depend on the host’s immune status. Toxoplasma/Toxoplasmosis
    • Malaria Malaria Malaria is an infectious parasitic disease affecting humans and other animals. Most commonly transmitted via the bite of a female Anopheles mosquito infected with microorganisms of the Plasmodium genus. Patients present with fever, chills, myalgia, headache, and diaphoresis. Plasmodium/Malaria
    • Chlamydia Chlamydia Chlamydiae are obligate intracellular gram-negative bacteria. They lack a peptidoglycan layer and are best visualized using Giemsa stain. The family of Chlamydiaceae comprises 3 pathogens that can infect humans: Chlamydia trachomatis, Chlamydia psittaci, and Chlamydia pneumoniae. Chlamydia trachomatis
  • Anatomic abnormalities:
    • Cervical insufficiency Cervical insufficiency Cervical dilation without contractions (not labor), due to structural weakness of the cervix Preterm Labor and Birth
    • Submucosal leiomyomas
    • Congenital Congenital Chorioretinitis uterine anomalies, e.g., septate 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
    • Intrauterine adhesions
  • Maternal chromosomal abnormalities
  • Recreational drug use

Fetal factors

  • Chromosomal abnormalities (account for 50% of all spontaneous abortions)
    • Autosomal trisomies
    • Turner syndrome Turner syndrome Turner syndrome is a genetic condition affecting women, in which 1 X chromosome is partly or completely missing. The classic result is the karyotype 45,XO with a female phenotype. Turner syndrome is associated with decreased sex hormone levels and is the most common cause of primary amenorrhea. Turner Syndrome ( monosomy Monosomy The condition in which one chromosome of a pair is missing. In a normally diploid cell it is represented symbolically as 2n-1. Types of Mutations X)
  • Congenital Congenital Chorioretinitis anomalies

Paternal factors

  • Increasing paternal age
  • Paternal chromosomal abnormalities

Miscellaneous

  • Trauma
  • Environmental exposure to toxins:
    • Tobacco
    • Chemotherapeutic agents
    • Certain industrial chemicals:
      • Toluene
      • Formaldehyde

Clinical Presentation and Diagnosis

Clinical presentation

  • Individuals may be asymptomatic.
  • The most common symptom, if present, is vaginal bleeding.
  • Other symptoms may include:
    • Abnormal vaginal discharge
    • Abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
    • Menstrual-like cramping

Diagnostic evaluation

The diagnosis is made by a combination of history, physical examination, and ultrasound findings.

  • Key features to evaluate on clinical examination:
    • Presence or absence of vaginal bleeding
    • Dilation of the cervical os
    • Hemodynamic stability
  • Key features to evaluate on ultrasound:
    • Presence of products of conception in 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
    • Presence or absence of fetal cardiac activity
    • Size of the gestational sac or fetus
  • Additional studies:
    • Check maternal blood type and Rh factor Rh Factor Blood Group Systems
    • CBC to evaluate for acute blood loss anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types
    • Beta-hCG levels

Clinical and ultrasound findings by type

The types of spontaneous abortions differ based on clinical examination and ultrasound findings.

Threatened abortion:

  • Vaginal bleeding is present.
  • Abdominal cramps Cramps Ion Channel Myopathy or pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways may be present.
  • Fetal cardiac activity is present.
  • Cervical os is closed.
  • Products of conception are not expelled.
  • Generally self-limiting Self-Limiting Meningitis in Children; prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas is worse with heavier bleeding.

Inevitable abortion:

  • Vaginal bleeding is present.
  • Abdominal cramps Cramps Ion Channel Myopathy and pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways may be present.
  • Fetal cardiac activity may be present.
  • Cervical os is dilated.
  • Products of conception are not expelled.

Incomplete abortion:

  • Vaginal bleeding is present.
  • Abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways is present.
  • Fetal cardiac activity may be present.
  • Cervical os is dilated.
  • POC is partially expelled.

Complete abortion:

  • Vaginal bleeding is often present.
  • Abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways may be present.
  • Cervical os is closed.
  • Products of conception are completely expelled.

Missed abortion:

  • Vaginal bleeding is often absent but may be present.
  • Abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways is often absent.
  • Fetal cardiac activity is absent.
  • Cervical os is closed.
  • Products of conception are not expelled.
Differences between types of spontaneous abortion

Differences between the types of spontaneous abortion:
Important differentiating factors include the presence or absence of vaginal bleeding, whether the cervical os is dilated or closed, the presence or absence of the products of conception, and fetal cardiac activity.

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Management

General approach

  • The appropriate therapy for spontaneous abortions depends on the type of abortion and hemodynamic stability of the individual.
  • Rh(D)-negative women should receive Rh(D) immunoglobulin if vaginal bleeding is present.
  • The 3 main options for therapy are expectant, medical, or surgical management.

Expectant management

  • Appropriate for hemodynamically stable individuals
  • Treatment of choice for threatened abortions
  • May involve avoiding intercourse and decreasing strenuous physical activities
  • Close follow-up with clinic visits and ultrasound is crucial.
  • May take weeks to resolve
  • In certain situations, surgical intervention may become necessary if expectant management fails.

Medical management

  • Appropriate for:
    • Hemodynamically stable individuals
    • Poor surgical candidates
  • May be used for inevitable, incomplete, or missed abortions
  • Involves pharmacological agents to aid in cervical dilation Cervical dilation A measurement of the diameter of the cervical canal, reported in centimeters Normal and Abnormal Labor and expulsion of the products of conception
    • Misoprostol Misoprostol A synthetic analog of natural prostaglandin e1. It produces a dose-related inhibition of gastric acid and pepsin secretion, and enhances mucosal resistance to injury. It is an effective anti-ulcer agent and also has oxytocic properties. Eicosanoids:
      • Given orally or vaginally
      • Prostaglandin E1 E1 An aromatized C18 steroid with a 3-hydroxyl group and a 17-ketone, a major mammalian estrogen. It is converted from androstenedione directly, or from testosterone via estradiol. In humans, it is produced primarily by the cyclic ovaries, placenta, and the adipose tissue of men and postmenopausal women. Noncontraceptive Estrogen and Progestins analog → uterotonic
    • Premedication may be given with mifepristone Mifepristone A progestational and glucocorticoid hormone antagonist. Its inhibition of progesterone induces bleeding during the luteal phase and in early pregnancy by releasing endogenous prostaglandins from the endometrium or decidua. As a glucocorticoid receptor antagonist, the drug has been used to treat hypercortisolism in patients with nonpituitary Cushing syndrome. Antiprogestins and Selective Progesterone Modulators:
      • Can increase efficacy
      • Competitively binds to progestin receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors → primes 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 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 for the effects of misoprostol Misoprostol A synthetic analog of natural prostaglandin e1. It produces a dose-related inhibition of gastric acid and pepsin secretion, and enhances mucosal resistance to injury. It is an effective anti-ulcer agent and also has oxytocic properties. Eicosanoids
  • Pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways control with NSAIDs NSAIDS Primary vs Secondary Headaches
  • Close follow-up is crucial to ensure the success of therapy.
  • May take days to weeks to resolve
  • Surgical management might be necessary if medical treatment fails.

Surgical management

  • Appropriate for:
    • Hemodynamically unstable individuals
    • Individuals who decline other management options
    • Individuals unable to adhere to a follow-up plan
    • Individuals who have not fully expelled the products of conception with expectant or medical management
  • Dilation and curettage Curettage A scraping, usually of the interior of a cavity or tract, for removal of new growth or other abnormal tissue, or to obtain material for tissue diagnosis. It is performed with a curet (curette), a spoon-shaped instrument designed for that purpose. Benign Bone Tumors is the preferred surgical intervention for abortions.
  • Resolves immediately after surgery.
  • Risks include:
    • Uterine perforation Perforation A pathological hole in an organ, blood vessel or other soft part of the body, occurring in the absence of external force. Esophagitis
    • Infection
    • Hemorrhage
    • Subsequent formation of uterine adhesions (also known as synechiae Synechiae Scar tissue from prior surgery. Infertility)

Differential Diagnosis

  • Septic abortion: a condition that may occur as a result of an infection in the setting of a missed, inevitable, or incomplete abortion. The infection typically starts as a localized infection of 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 and then spreads systemically. The diagnosis is clinical and should be suspected in women with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, uterine pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, tenderness, and vaginal bleeding before or after pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care loss. The definitive treatment, in addition to broad-spectrum Broad-Spectrum Fluoroquinolones antibiotics, is the prompt evacuation of 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 using dilation and curettage Curettage A scraping, usually of the interior of a cavity or tract, for removal of new growth or other abnormal tissue, or to obtain material for tissue diagnosis. It is performed with a curet (curette), a spoon-shaped instrument designed for that purpose. Benign Bone Tumors.
  • Ectopic pregnancy Ectopic pregnancy Ectopic pregnancy refers to the implantation of a fertilized egg (embryo) outside the uterine cavity. The main cause is disruption of the normal anatomy of the fallopian tube. Ectopic Pregnancy: implantation Implantation Endometrial implantation of embryo, mammalian at the blastocyst stage. Fertilization and First Week of a fertilized egg ( embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week) outside the uterine cavity. The main cause of ectopic pregnancy Ectopic pregnancy Ectopic pregnancy refers to the implantation of a fertilized egg (embryo) outside the uterine cavity. The main cause is disruption of the normal anatomy of the fallopian tube. Ectopic Pregnancy is disruption of the normal anatomy of the fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Uterus, Cervix, and Fallopian Tubes: Anatomy. Consequently, affected individuals may suffer from acute abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and vaginal bleeding as the developing embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week increases in size. Ultrasound and determination of beta-hCG levels are used in the diagnosis. Management depends on the condition of the individual and is usually medical or surgical. Severe cases involving rupture of the fallopian tube Fallopian Tube A pair of highly specialized canals extending from the uterus to its corresponding ovary. They provide the means for ovum transport from the ovaries and they are the site of the ovum’s final maturation and fertilization. The fallopian tube consists of an interstitium, an isthmus, an ampulla, an infundibulum, and fimbriae. Its wall consists of three layers: serous, muscular, and an internal mucosal layer lined with both ciliated and secretory cells. Uterus, Cervix, and Fallopian Tubes: Anatomy and hemorrhage are considered surgical emergencies.
  • Hydatidiform mole Mole Nevi (singular nevus), also known as “moles,” are benign neoplasms of the skin. Nevus is a non-specific medical term because it encompasses both congenital and acquired lesions, hyper- and hypopigmented lesions, and raised or flat lesions. Nevus/Nevi (molar pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care): a gestational trophoblastic disease Gestational trophoblastic disease Gestational trophoblastic diseases are a spectrum of placental disorders resulting from abnormal placental trophoblastic growth. These disorders range from benign molar pregnancies (complete and partial moles) to neoplastic conditions such as invasive moles and choriocarcinoma. Gestational Trophoblastic Disease arising from 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. These premalignant tumors are classified as complete (no fetal tissue, diploid Diploid The chromosomal constitution of cells, in which each type of chromosome is represented twice. Symbol: 2n or 2x. Basic Terms of Genetics) or partial (some fetal tissue, triploid). The presentation is more severe with a complete mole Mole Nevi (singular nevus), also known as “moles,” are benign neoplasms of the skin. Nevus is a non-specific medical term because it encompasses both congenital and acquired lesions, hyper- and hypopigmented lesions, and raised or flat lesions. Nevus/Nevi, and women may present with 1st-trimester vaginal bleeding, nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics, and preeclampsia Preeclampsia A complication of pregnancy, characterized by a complex of symptoms including maternal hypertension and proteinuria with or without pathological edema. Symptoms may range between mild and severe. Pre-eclampsia usually occurs after the 20th week of gestation, but may develop before this time in the presence of trophoblastic disease. Hypertensive Pregnancy Disorders. Diagnosis is based on high beta-hCG levels and by using ultrasound, which may show the characteristic “snowstorm” appearance with a complete mole Mole Nevi (singular nevus), also known as “moles,” are benign neoplasms of the skin. Nevus is a non-specific medical term because it encompasses both congenital and acquired lesions, hyper- and hypopigmented lesions, and raised or flat lesions. Nevus/Nevi. Surgical removal of the molar pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care is needed.

References

  1. Cunningham, F.G. (2018). Abortion. In Spong, C.Y: (Ed.), Williams Obstetrics. (25th ed., pp. 344–348). New York: Mcgraw Hill Medical.
  2. Gabbe, S.G. (2017). Pregnancy Loss. In Gabbe, S. (Ed.), Obstetrics Normal and Problem Pregnancies. (6th ed., pp. 592–608). Elsevier. 
  3. Prager, S., Micks, E., Dalton, V.K. (2021). Pregnancy loss (miscarriage): Terminology, risk factors, and etiology. UpToDate. Retrieved September 2, 2021, from https://www.uptodate.com/contents/pregnancy-loss-miscarriage-terminology-risk-factors-and-etiology
  4. Prager, S., Micks, E., Dalton, V.K. (2021). Pregnancy loss (miscarriage): Clinical presentations, diagnosis, and initial evaluation. UpToDate. Retrieved September 2, 2021, from https://www.uptodate.com/contents/pregnancy-loss-miscarriage-clinical-presentations-diagnosis-and-initial-evaluation
  5. Dulay, A.T. (2020). Spontaneous abortion. [online] MSD Manual Professional Version. Retrieved September 2, 2021, from https://www.msdmanuals.com/professional/gynecology-and-obstetrics/abnormalities-of-pregnancy/spontaneous-abortion

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