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Questions and Answers
What is the chromosomal composition in males?
Trisomy 16 is the most common trisomy leading to live births.
False
What condition is characterized by an extra chromosome on chromosome 21?
Down syndrome
The condition resulting from having one less chromosome than normal is called ______.
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Match the following syndromes to their respective chromosome trisomies:
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What is the purpose of the Non-Stress Test (NST)?
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The Non-Stress Test (NST) should be performed if the pregnant woman has not eaten a meal beforehand.
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What position should a pregnant woman be in during the Non-Stress Test (NST)?
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The upper graph in a cardiotocography (CTG) display shows fetal ______ rates.
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Match the following components of the Non-Stress Test (NST) with their functions:
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What is the sensitivity of Non-Invasive Prenatal Test (NIPT)?
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The integrated screening process combines the first and second trimester screenings.
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What are the two types of diagnostic tests mentioned for positive screening results?
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The source of cell-free DNA for Non-Invasive Prenatal Testing comes from the __________ of placental cells.
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Match the following results from the screening with their corresponding cut-off values:
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What is the gestation period considered for screening for Down syndrome in the first trimester?
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The dual test includes the measurement of PAPP-A and hCG levels.
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What is the recommended action if the dual test indicates a positive result for Down syndrome?
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If a previous baby had Down syndrome due to a balanced translocation, the risk for the current pregnancy is _______.
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Match the biochemical findings with their corresponding risk for trisomy 21:
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What is the normal value for Nuchal Translucency (NT)?
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Nuchal Translucency measurement is taken when the crown-rump length (CRL) is between 30-60mm.
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Name one condition associated with an enlarged Nuchal Translucency.
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The Nuchal Translucency region should be measured in the __________ plane.
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Match the following conditions with their associated features:
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Which diagnostic test is used to further evaluate NT measurements of ≥ 3mm?
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Cystic hygroma is less reliable than Nuchal Translucency as a marker for aneuploidy.
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What condition is indicated by a Nuchal Translucency measurement of 23mm?
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What is the primary indication for performing an amniocentesis?
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Fetal blood sampling is a routinely used procedure for prenatal diagnosis.
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What is the common alternative name for fetal blood sampling?
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Amniocentesis is performed using a ______ gauge spinal needle.
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Match the following diagnostic indications with their respective procedures:
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What is a common indication for prenatal diagnosis?
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Amniocentesis can be performed during the first trimester of pregnancy.
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Name one condition that may lead to a parent being a carrier for genetic disorders.
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Chorionic Villi Sampling is typically performed between __________ weeks of gestation.
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Match the prenatal invasive tests to their ideal timing:
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What is the normal range for baseline fetal heart rate?
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Bradycardia is defined as a fetal heart rate of less than 110 bpm.
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What does absent variability in fetal heart rate indicate?
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A fetal heart rate acceleration is defined as an increase in FHR by _____ bpm for _____ seconds.
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Match the conditions with their implications based on the sinusoidal heart wave pattern:
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Which of the following is a soft tissue marker indicative of screening results in pregnancy?
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The quad test includes additional markers compared to the triple test, specifically Inhibin A.
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What is the detection rate of the quad test for Down syndrome?
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The absence of ____________ is a marker that may indicate Down syndrome during screening.
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Match the following ultrasound findings with their descriptions:
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Which conditions are indications for antepartum fetal monitoring? (Select all that apply)
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Fetal movement counting is only recommended for women in their second trimester.
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What is the normal fetal movement count when resting in the left lateral position?
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The beginning of perception of fetal movement, known as quickening, typically occurs at ______ weeks for primiparous women.
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Match the fetal surveillance tests with their primary purposes:
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Study Notes
Aneuploidy
- Defect in chromosome numbers
- Triploidy: 69 chromosomes
- Trisomy: 47 chromosomes (one extra chromosome)
- Monosomy: 45 chromosomes (one less chromosome)
- Gametes are haploid (23 chromosomes)
- Normal diploid cells:
- Male: 44 chromosomes + XY
- Female: 44 chromosomes + XX
- Common trisomies:
- Trisomy 21: Down syndrome
- Trisomy 18: Edwards' syndrome
- Most common trisomy leading to abortion is trisomy 16.
Down Syndrome
- Most viable trisomy
- Most common outcome: Abortion
- Causes:
- Nondisjunction of chromosome (95%): Non-inheritable
- Translocation of chromosome (4%): Inheritable
- Most common between 14 and 21 years
- Balanced translocation
- Chances of Down syndrome increase with increasing maternal age
- Recurrence chances:
- Mother: 10-15%
- Father: 5%
- Mosaicism (1%): Inheritable
Diagnostic Algorithm for Aneuploidy Screening
- Secondary screening test:
- Non-invasive prenatal test (NIPT):
- Sample: Cell-free fetal DNA (maternal blood)
- Source: Apoptosis of placental cells (syncitiotrophoblast)
- Period of Gestation (POG): 210 weeks
- Sensitivity: 99%
- Disadvantages: Not diagnostic, expensive
- Can detect: Trisomy 21, 18, 13, and some sex chromosomal abnormalities
- Non-invasive prenatal test (NIPT):
- Positive NIPT Result:
- Diagnostic test (invasive): Karyotyping
- 1st trimester: Chorionic villus sampling
- 2nd trimester: Amniocentesis
- Diagnostic test (invasive): Karyotyping
- Negative NIPT Result:
- No need for karyotyping
- Integrated screening:
- First trimester screening + Second trimester screening
- 1-step screening process:
- 1st trimester: Dual test + NT
- 2nd trimester: Quad test
- Drawbacks: T₁ screening results are withheld until T₂ screening is done
- Sensitivity: 85-95%
- Screening results are given as a ratio
- Cut-off values:
- Trisomy 18/13: 1:100
- Down syndrome: 1:250
- Interpretation: Indicates that in 1 out of 250 pregnancies with the same findings as the patient, Down syndrome is present.
Management of Decreased Fetal Movement
- Antepartum Fetal Monitoring:
- Modified Biophysical Score:
- Amniotic fluid assessment + Non-Stress Test (NST)
- Modified Biophysical Score:
- if Biophysical Score not possible, perform NST
- Non-Stress Test (NST):
- Device used: External cardiotocography machine
- 2 Transducers
- 1 Bell
- 1 Monitor
- Procedure:
- Lie pregnant woman in the left lateral position for 20 minutes
- Attach transducers and bell to the abdomen with a belt
- Instruct her to press the bell on perception of fetal movement
- Record the same on NST strip (depicted by arrows)
- Avoid if the female has not eaten a meal, as hypoglycemia affects results. Give glucose prior.
- NST: Only FHR graph with arrows at fetal movement
- CTG:
- Upper graph: FHR
- Lower graph: Uterine contractions
- Device used: External cardiotocography machine
- Screening tests:
- If not possible: Biophysical score (Diagnostic test)
- Fetal heart rate (FHR):
- Not used in NST due to no contractions.
Ultrasound Examination - Nuchal Translucency (NT)
- Nuchal Translucency:
- Definition: Fluid-filled area behind the fetal neck, visible in ultrasound imaging
- Normal Value: Less than 3mm
- NT ≥ 3mm: Indicates potential risk for various conditions, requiring further evaluation
- Potential Conditions associated with Enlarged NT:
- Aneuploidy:
- Down syndrome (most common): Trisomy 21
- Turner syndrome/monosomy X
- Trisomy 13 & 18
- Congenital Heart Disease
- Diaphragmatic hernia
- Genetic syndromes:
- Noonan syndrome
- DiGeorge syndrome
- Twin-to-twin transfusion syndrome
- Aneuploidy:
- Measurement Parameters:
- Fetal Position: Neutral head position
- Plane: Mid-sagittal plane
- Amnion: Clearly visible
- CRL: 45-84mm
- Measurement: Widest area from inner border to inner border
- Diagnostic Algorithm:
- NT ≥ 3mm: Requires further diagnostic testing (karyotyping)
- Aneuploidy ruled out: Further examination of fetal features to rule out congenital heart disease
- Cystic Hygroma:
- Marker: Potentially better marker of aneuploidy than NT
- Associated Conditions: Often seen in aneuploidy, such as Trisomy 21, 18, 13, or Turner syndrome, and other congenital heart conditions
- Timing of Detection:
- 1st trimester detection: Increased risk of Down syndrome
- 2nd trimester detection: Increased risk of Turner syndrome
Normal Pregnancy and Antenatal Care - Down Syndrome Screening
- Universal screening: All pregnant females, regardless of age
- Previous Down Syndrome in Baby: Diagnostic testing (karyotyping or NIPT) is preferred
- Screening in First Trimester:
- Gestation Period (POG): 11-13 weeks + 6 days
- CRL (Crown-Rump Length): 45mm to 84mm
- Biochemical Test:
- Dual Test:
- PAPP-A: Pregnancy-associated plasma protein A
- hCG: Human chorionic gonadotropin
- Combined Test:
- Dual test + Nuchal translucency
- Dual Test:
- In Twin Pregnancy:
- Sensitivity: Combined test > Dual Test
- If Dual test is Positive: Further testing (USG Nuchal translucency)
- If Findings are Normal: No karyotyping needed
- If Findings are Abnormal: Karyotyping needed
- If Decreased PAPP-A and Increased hCG are observed: Increased risk of fetal growth restriction. May develop IUGR (Intrauterine Growth Restriction).
- Important Considerations:
- Exception: If a previous baby had Down syndrome due to a balanced translocation, the risk is 100%
Aneuploidy Screening
- Amniocentesis:
- Procedure: Performed under ultrasound guidance using a spinal needle to collect amniotic fluid
- Diagnostic Indications:
- Aneuploidy
- Fetal viral infections
- Suspected neural tube defects
- Therapeutic Indications:
- Polyhydramnios
- Hemolytic disease of the fetus
- Fetal Blood Sampling:
- AKA: Cordocentesis/PUBS (Periumbilical Fetal Blood Sampling)
- Procedure: Usually involves sampling from the umbilical vein (alternate source: portal vein)
- Sample: Umbilical vein
- Diagnostic Indications:
- Measure fetal hemoglobin (Hb) and hematocrit (Hct) for anemia
- Limitations: Fetal loss rate of ~2.1%
- Rh isoimmunized pregnancies are one instance where fetal blood sampling might be considered
- Common heart defects associated with Down syndrome include endocardial cushion defects, ventricular septal defects (VSD), and atrial septal defects (ASD).
Prenatal Diagnosis
- Indication:
- Positive screening for aneuploidy → Karyotyping or Fluorescent In-Situ Hybridization (FISH)
- History of previous child with chromosomal anomaly
- Either parent carrier:
- Balanced translocation
- Single gene disorders (e.g., Hemoglobinopathies, Sickle cell disease)
- Suspected/confirmed viral infection in pregnancy → PCR of amniotic fluid
- Invasive Prenatal Test:
- Chorionic Villi Sampling vs. Amniocentesis vs. Cordocentesis:
Feature Chorionic Villi Sampling Amniocentesis Cordocentesis Study Material Cytotrophoblast > Trophoblast Amniocytes > Dermal fibroblast - Ideal Time 10-14 weeks; 11-13 weeks + 6 days 15-20 weeks; 16-18 weeks - Fetal Loss (%) 0.5-1% 0.5-1% 2.1%
- Chorionic Villi Sampling vs. Amniocentesis vs. Cordocentesis:
Terminology used in NST
- Baseline fetal heart rate: Minimum 10 minutes taken into consideration
- Normal: 110 to 160 bpm
- Bradycardia: < 110 bpm
- Tachycardia: > 160 bpm
- Baseline variability:
- FHR is variable by 5 to 25 bpm
- Variability < 5 bpm indicates fetal hypoxia (bad prognosis)
- Absent/Decreased variability
- Sinusoidal heart wave pattern:
- Indicates:
- Fetal anemia d/t Parvovirus B19, Rh incompatibility, Vasa previa
- Severe hypoxia
- Acidosis
- Management: Immediate Cesarean section d/t bad prognosis.
- Indicates:
- Fetal heart rate acceleration:
- Definition: ↑ in FHR by 15 bpm for 15 sec with fetal movements
- Principle:
Normal Fetus Compromised Fetus FHR Acceleration FHR acceleration (indicates normal fetal autonomic nervous system) Normal FHR, no acceleration - If NST done between 30 to 31 weeks:
- FHR acceleration: ↑ FHR by 10 bpm for 10 sec with fetal movements
- Causes of absent FHR acceleration:
- Maternal narcotic use
- Fetal sleep
- Fetal hypoxia
- Fetal acidosis
- Sepsis
Normal Pregnancy and Antenatal Care
- Other Markers:
- USG: Absent nasal bone
- Doppler:
- Abnormal flow in ductus venosus
- Tricuspid regurgitation
- Nuchal translucency can be confused with cystic hygroma:
Cystic hygroma Nuchal translucency Amount of fluid More Comparatively less Extent Widespread Limited to neck Septa +/- -
Screening in Second Trimester
- POG: 16 to 18 weeks
- Investigations:
- Biochemical test:
- Triple test (AKA Bart's/Kettering test):
Down syndrome AFP ↓ HCG ↑ Unconjugated E3 (estriol) ↓ - Quad test:
- Detection rate: 80%
- markers: Triple test + Inhibin A (↑ in Down syndrome)
- Triple test (AKA Bart's/Kettering test):
- Ultrasound:
- ≥ 2 soft tissue markers (+ve screening)
- Soft tissue markers (STM):
- Nuchal skin fold thickness (NSFT): ≥6mm
- Hypoplastic/absent nasal bone
- Short femur (SF)
- Short humerus
- Echogenic intracardiac focus
- Simian crease
- If single STM +ve:
- Highest risk of aneuploidy: NSFT > SF
- Lowest risk of aneuploidy: CPC
- 11-17%: Normal fetus
- Other Findings:
- Hyperechoic bowel
- Duodenal atresia
- Pyelectasis
- Sandal gap
- Choroid plexus cyst (CPC)
- Aberrant right subclavian artery
- Biochemical test:
Antepartum Fetal Monitoring
- Indications for antepartum fetal monitoring:
- All high-risk pregnancies at 32 weeks
- Reduced fetal movements
- Pregnancies ≥ 40 weeks with reduced amniotic fluid
- Previous history of adverse pregnancy outcomes (started 2 weeks prior to adverse outcome)
- Tests for fetal surveillance:
- Daily fetal movement count: All pregnant women in the third trimester
- Non-stress test/ VAST (Vibro-acoustic stimulation test)
- Ultrasound (USG): Amniotic fluid assessment
- Biophysical score (Manning score)
- Doppler studies
- Contraction stress test (Outdated)
- Cardiotocography and Non-stress test (NST) are performed using the same device during both intra-partum and ante-natal periods.
- Fetal Movement Count:
- Quickening:
- The beginning of perception of fetal movement occurs at:
- 18 to 20 weeks in primiparous
- 16 to 18 weeks in multiparous
- The beginning of perception of fetal movement occurs at:
- Method: Fetal movements are counted after breakfast, lunch, and dinner
- Cardiff count of 10: Used for assessing the fetal movement count
- Normal count:
- At rest: 10 movements over 1 hour (lying in left lateral position)
- During normal activity: 10 movements over 12 hours
- Causes of decreased fetal movement:
- Fetal hypoxia
- Placental dysfunction ➡️ Intrauterine fetal death
- Quickening:
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Description
This quiz explores the concepts of aneuploidy, including definitions and examples such as triploidy, trisomy, and monosomy. It also details Down syndrome, its causes, diagnostic approaches, and the implications of maternal age on its occurrence. Test your understanding of these crucial genetic topics.
