The primary goals of antepartum testing and monitoring are to assess fetal well-being, identify treatable situations that may cause complications, and evaluate for chromosomal abnormalities. Antepartum tests for aneuploidy are typically performed in the 1st and 2nd trimesters. These tests are divided into screening tests Screening tests Screening tests are used to identify people in the early stages of a disease and enable early intervention with the goal of reducing morbidity and mortality. Epidemiological Values of Diagnostic Tests (which include cell-free DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure testing, serum analyte Analyte The molecule of interest (antigen) Immunoassays testing, and nuchal translucency Nuchal translucency A prenatal ultrasonography measurement of the soft tissue behind the fetal neck. Either the translucent area below the skin in the back of the fetal neck (nuchal translucency) or the distance between occipital bone to the outer skin line (nuchal fold) is measured. Obstetric Imaging measurements), and diagnostic tests Diagnostic tests Diagnostic tests are important aspects in making a diagnosis. Some of the most important epidemiological values of diagnostic tests include sensitivity and specificity, false positives and false negatives, positive and negative predictive values, likelihood ratios, and pre-test and post-test probabilities. Epidemiological Values of Diagnostic Tests, which provide a definitive diagnosis of aneuploidy and include chorionic villus sampling (CVS) and amniocentesis Amniocentesis Percutaneous transabdominal puncture of the uterus during pregnancy to obtain amniotic fluid. It is commonly used for fetal karyotype determination in order to diagnose abnormal fetal conditions. Polyhydramnios. Antepartum monitoring is done in the 2nd and 3rd trimesters to evaluate fetal well-being and assess the risk of fetal death. Antepartum monitoring tests include continuous cardiotocography (i.e., fetal heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology tracings), the non-stress and contraction stress tests (NST and CST, respectively), the fetal biophysical profile Biophysical Profile Obstetric Imaging (BPP), and umbilical artery Umbilical artery Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the fetus to the mother via the placenta. In humans, there are usually two umbilical arteries but sometimes one. Prenatal and Postnatal Physiology of the Neonate Doppler Doppler Ultrasonography applying the doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. Ultrasound (Sonography) studies.
Last updated: 10 May, 2022
Antepartum testing
Antepartum monitoring
There are many indications for fetal monitoring and/or screening Screening Preoperative Care, including:
Maternal indications
Fetal indications
All pregnant women should have certain screening Screening Preoperative Care laboratory tests and imaging studies done at different points during the 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, including:
At the 1st OB appointment:
Other testing
Overview
Cell-free fetal DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure testing
1st-trimester screening Screening Preoperative Care for aneuploidy
Condition | hCG | PAPP-A | Nuchal translucency Nuchal translucency A prenatal ultrasonography measurement of the soft tissue behind the fetal neck. Either the translucent area below the skin in the back of the fetal neck (nuchal translucency) or the distance between occipital bone to the outer skin line (nuchal fold) is measured. Obstetric Imaging |
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Trisomy Trisomy The possession of a third chromosome of any one type in an otherwise diploid cell. Types of Mutations 21 | ↑ | ↓↓ | ↑↑ |
Trisomy 18 Trisomy 18 Edwards syndrome, or trisomy 18, is a genetic syndrome caused by the presence of an extra chromosome 18. The extra chromosome is either from 3 full copies of chromosome 18 or an additional segment of chromosome 18. As the 2nd most common trisomy, Edwards syndrome is seen in 1 out of every 5,500 live births. Edwards Syndrome (Trisomy 18) | ↓↓ | ↓↓ | ↑↑ |
Trisomy 13 Trisomy 13 Trisomy 13, or Patau syndrome, is a genetic syndrome caused by the presence of 3 copies of chromosome 13. As the 3rd most common trisomy, Patau syndrome has an incidence of 1 in 10,000 live births. Most cases of Patau syndrome are diagnosed prenatally by maternal screening and ultrasound. More than half of the pregnancies result in spontaneous abortions. Patau Syndrome (Trisomy 13) | ↓ | ↓↓ | ↑ |
Quadruple screen ( quad screen Quad Screen Prenatal Care)
Condition | hCG | AFP AFP The first alpha-globulins to appear in mammalian sera during fetal development and the dominant serum proteins in early embryonic life. Hepatocellular Carcinoma (HCC) and Liver Metastases | Estriol Estriol A hydroxylated metabolite of estradiol or estrogen that has a hydroxyl group at C3, 16-alpha, and 17-beta position. Estriol is a major urinary estrogen. During pregnancy, a large amount of estriol is produced by the placenta. Isomers with inversion of the hydroxyl group or groups are called epiestriol. Noncontraceptive Estrogen and Progestins | Inhibin A Inhibin A Glycoproteins that inhibit pituitary follicle stimulating hormone secretion. Inhibins are secreted by the sertoli cells of the testes, the granulosa cells of the ovarian follicles, the placenta, and other tissues. Inhibins and activins are modulators of follicle stimulating hormone secretions; both groups belong to the TGF-beta superfamily, as the transforming growth factor beta. Inhibins consist of a disulfide-linked heterodimer with a unique alpha linked to either a beta a or a beta B subunit to form inhibin a or inhibin b, respectively. Menstrual Cycle |
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Trisomy Trisomy The possession of a third chromosome of any one type in an otherwise diploid cell. Types of Mutations 21 | ↑ | ↓ | ↓ | ↑ |
Trisomy 18 Trisomy 18 Edwards syndrome, or trisomy 18, is a genetic syndrome caused by the presence of an extra chromosome 18. The extra chromosome is either from 3 full copies of chromosome 18 or an additional segment of chromosome 18. As the 2nd most common trisomy, Edwards syndrome is seen in 1 out of every 5,500 live births. Edwards Syndrome (Trisomy 18) | ↓↓ | ↓ | ↓↓ | ↔ |
Integrated testing:
Diagnostic testing is invasive and involves sampling the chorionic villi Chorionic villi Threadlike vascular projections of the chorion. Chorionic villi may be free or embedded within the decidua forming the site for exchange of substances between fetal and maternal blood (placenta). Placenta, Umbilical Cord, and Amniotic Cavity or 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 for fetal tissue that can be used directly for genetic testing Genetic Testing Detection of a mutation; genotype; karyotype; or specific alleles associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Myotonic Dystrophies.
Illustration representing the amniocentesis Amniocentesis Percutaneous transabdominal puncture of the uterus during pregnancy to obtain amniotic fluid. It is commonly used for fetal karyotype determination in order to diagnose abnormal fetal conditions. Polyhydramnios procedure
Image by Lecturio.The only relative contraindications Contraindications A condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks). Noninvasive Ventilation for both procedures include:
Potential complications are similar for both CVS and amniocentesis Amniocentesis Percutaneous transabdominal puncture of the uterus during pregnancy to obtain amniotic fluid. It is commonly used for fetal karyotype determination in order to diagnose abnormal fetal conditions. Polyhydramnios and include:
Cardiotocography is used to monitor the fetal heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology (FHR) and contractions plotted over real time, usually via abdominal ultrasonography and pressure transducers, respectively. Fetal heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology is recorded in the top panel and contractions in the lower panel of the tracing.
There are 5 major components that should be evaluated when interpreting a cardiotocography tracing:
Early decelerations:
Note how the nadir of the
deceleration
Deceleration
A decrease in the rate of speed.
Blunt Chest Trauma is aligned with the peak of the contractions.
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 decelerations:
These 1st 2
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 decelerations are a concern because of how low they go (down to < 60/min) and how long they last (nearly a full minute). The 3rd
deceleration
Deceleration
A decrease in the rate of speed.
Blunt Chest Trauma is shallower and shorter, and, if seen without any other decelerations and in combination with moderate variability and/or accelerations, would be less worrisome.
Late decelerations:
Note how the nadir of these decelerations follows the peak of the contraction, which indicates
uteroplacental insufficiency
Uteroplacental Insufficiency
Uteroplacental insufficiency may be acute or chronic and refers to the inability of the placenta to deliver a sufficient supply of O2 and nutrients to the fetus
Placental Abnormalities, which requires intervention.
Characteristics of a continuous FHR tracing are assessed periodically and used to classify tracings into 1 of 3 categories. These categories provide some prognostic information on the current status of fetal well-being and can help guide management.
Category I: normal
Category I (normal) fetal
heart rate
Heart rate
The number of times the heart ventricles contract per unit of time, usually per minute.
Cardiac Physiology tracing
An FHR baseline of 150/min, moderate variability, several accelerations, and no decelerations are seen. Three contractions are shown; if these contractions were measured using an intrauterine pressure catheter, they each reach approximately 60 Montevideo units (MVUs), for a total of 180 MVUs in the 8 minutes shown. Based on this pattern, there would likely be a 4th contraction near the 10-minute mark, making this contraction pattern adequate (defined as > 200 MVUs per 10 minutes) to induce cervical change.
Category II: indeterminate
Category II fetal
heart rate
Heart rate
The number of times the heart ventricles contract per unit of time, usually per minute.
Cardiac Physiology tracing, which is indeterminate:
The baseline is normal, but there is minimal variability. There are no decelerations or accelerations in this tracing.
Category III: abnormal
Fetal
heart rate
Heart rate
The number of times the heart ventricles contract per unit of time, usually per minute.
Cardiac Physiology tracing demonstrating a prolonged late
deceleration
Deceleration
A decrease in the rate of speed.
Blunt Chest Trauma:
Variability appears moderate, however, and there is a spontaneous return to baseline. If this pattern continues, this is a worrisome tracing, demonstrating fetal distress.
An NST is cardiotocometry performed for 20 minutes (or longer if needed) to assess antepartum fetal well-being, usually after 28 weeks. Non-stress tests are classified as either reactive or nonreactive rather than by categories used to describe continuous fetal monitoring.
Reactive NST
Nonreactive NST
A CST is similar to an NST but is performed with induced (e.g., with pitocin) or spontaneous contractions, which allows providers to assess the impacts of the contractions on the FHR pattern. Interpretations include:
Component | Minimal normal criteria (observation for 30 minutes) | Score |
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Non-stress test | Reactive pattern (≥ 2 episodes of FHR accelerations of ≥ 15/min and ≥ 15 seconds within 20 minutes) | 2 |
Fetal movement | ≥ 3 discrete body or limb movements | 2 |
Fetal breathing | ≥ 1 rhythmic breathing episode(s) lasting ≥ 30 seconds | 2 |
Fetal tone | ≥ 1 episode(s) of a fetal extremity or 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 extension Extension Examination of the Upper Limbs with return to flexion Flexion Examination of the Upper Limbs | 2 |
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 volume | A single deepest vertical pocket ≥ 2 cm with a horizontal dimension ≥ 1 cm | 2 |
Umbilical artery Umbilical artery Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the fetus to the mother via the placenta. In humans, there are usually two umbilical arteries but sometimes one. Prenatal and Postnatal Physiology of the Neonate (UA) Doppler Doppler Ultrasonography applying the doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. Ultrasound (Sonography) studies (done on ultrasound machines) are used to help assess fetal well-being in pregnancies affected by fetal growth restriction Fetal growth restriction Fetal growth restriction (FGR), also known as intrauterine fetal growth restriction (IUGR), is an estimated fetal weight (EFW) or abdominal circumference < 10th percentile for gestational age. The term small for gestational age (SGA) is sometimes erroneously used interchangeably with FGR. Fetal Growth Restriction ( FGR FGR Fetal growth restriction (FGR), also known as intrauterine fetal growth restriction (IUGR), is an estimated fetal weight (EFW) or abdominal circumference < 10th percentile for gestational age. The term small for gestational age (sga) is sometimes erroneously used interchangeably with FGR. Fetal Growth Restriction).
Color
Doppler
Doppler
Ultrasonography applying the doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow.
Ultrasound (Sonography) of the
umbilical artery
Umbilical artery
Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the fetus to the mother via the placenta. In humans, there are usually two umbilical arteries but sometimes one.
Prenatal and Postnatal Physiology of the Neonate:
The scan shows a normal
umbilical artery
Umbilical artery
Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the fetus to the mother via the placenta. In humans, there are usually two umbilical arteries but sometimes one.
Prenatal and Postnatal Physiology of the Neonate waveform pattern in the bottom portion of the image. The peak of the waveforms represent systolic
flow
Flow
Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls.
Vascular Resistance, Flow, and Mean Arterial Pressure, while the trough of the waveforms represent end diastolic
flow
Flow
Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls.
Vascular Resistance, Flow, and Mean Arterial Pressure.
Abnormal umbilical artery Umbilical artery Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the fetus to the mother via the placenta. In humans, there are usually two umbilical arteries but sometimes one. Prenatal and Postnatal Physiology of the Neonate waveform patterns showing (a) markedly reduced diastolic flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure, (b) absent diastolic flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure, and (c) reverse diastolic flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure
Image: “Abnormal umbilical artery Umbilical artery Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the fetus to the mother via the placenta. In humans, there are usually two umbilical arteries but sometimes one. Prenatal and Postnatal Physiology of the Neonate waveform patterns” by Bano S, Chaudhary V, Pande S, Mehta V, Sharma A. License: CC BY 2.0