Prenatal Care Practice Questions

Q: A 25-year-old pregnant woman, at 16 weeks of gestation, presents with a positive screening test for a fetal neural tube defect. Ultrasound reveals a 3-cm neural tube defect in the thoracic spine. Which serum protein is measured in the screening test administered to the mother?

Alpha-fetoprotein. **Explanation:** The correct answer is **Alpha-fetoprotein (AFP)**. **1. Why Alpha-fetoprotein is correct:** AFP is a glycoprotein synthesized initially by the fetal yolk sac and later by the fetal liver. It is the fetal analog of albumin. In a normal fetus, small amounts of AFP leak into the amniotic fluid and cross the placenta into the maternal circulation. However, when there is an **Open Neural Tube Defect (ONTD)**, such as spina bifida or anencephaly, the fetal skin is not intact. This allows large amounts of AFP to leak directly from the fetal serum/cerebrospinal fluid into the amniotic fluid, subsequently leading to elevated **Maternal Serum Alpha-fetoprotein (MSAFP)** levels. Screening is typically performed between **15 and 20 weeks** of gestation. **2. Why the other options are incorrect:** * **Albumin:** While it is the major plasma protein in adults, it is not used as a biomarker for fetal structural defects. * **Bilirubin:** Amniotic fluid bilirubin levels (measured via $\Delta OD_{450}$) are used to monitor fetal hemolysis in Rh isoimmunization, not neural tube defects. * **Chromogranin:** This is a marker for neuroendocrine tumors (e.g., pheochromocytoma, carcinoid tumors) and has no role in prenatal screening. **3. NEET-PG High-Yield Pearls:** * **Most common cause of elevated MSAFP:** Underestimation of gestational age (dating error). Always re-evaluate dates with ultrasound first. * **Other causes of high MSAFP:** Multiple gestations, abdominal wall defects (omphalocele/gastroschisis), and fetal demise. * **Low MSAFP:** Associated with **Down Syndrome (Trisomy 21)** and Trisomy 18. * **Confirmatory Test:** If ultrasound is inconclusive, amniocentesis is done to check for elevated **Amniotic Fluid AFP** and the presence of **Acetylcholinesterase (AChE)**. AChE is highly specific for open neural tube defects.

Q: Cardiac activity of the fetus is typically seen by ultrasound by which gestational week?

6 weeks. **Explanation:** The fetal heart is the first functional organ to develop. In a normal pregnancy, cardiac activity can be visualized via **Transvaginal Sonography (TVS)** when the crown-rump length (CRL) is approximately 2–5 mm, which typically corresponds to **6 weeks of gestation** (calculated from the first day of the last menstrual period). **Why Option C is correct:** By the 6th week, the primitive heart tube has undergone looping and begins rhythmic contractions. On TVS, the "fetal pole" becomes visible adjacent to the yolk sac, and the flickering of the heart is the definitive sign of a viable intrauterine pregnancy. **Analysis of Incorrect Options:** * **4 weeks:** At this stage, the blastocyst has just implanted. Ultrasound may show a thickened endometrium (decidual reaction) but no gestational sac is visible. * **5 weeks:** The gestational sac first appears (at ~4.5 weeks), followed by the yolk sac (at ~5 weeks). While the heart begins to beat at the end of the 5th week, it is usually too small to be consistently detected by routine ultrasound. * **7 weeks:** While cardiac activity is clearly visible at 7 weeks, it is "typically" first detected by the 6th week. Waiting until 7 weeks is more common for Transabdominal Sonography (TAS), which has lower resolution than TVS. **NEET-PG High-Yield Pearls:** 1. **Order of appearance on TVS:** Gestational sac (4.5–5 weeks) → Yolk sac (5 weeks) → Fetal pole with cardiac activity (6 weeks). 2. **Discriminatory Zone:** Cardiac activity should always be seen when the CRL is **≥7 mm**. If CRL is ≥7 mm and no heartbeat is seen, it is diagnostic of pregnancy failure (Missed Abortion). 3. **Mean Sac Diameter (MSD):** A yolk sac should be seen when MSD is 8 mm; an embryo should be seen when MSD is 25 mm. 4. **Heart Rate:** At 6 weeks, the normal fetal heart rate is approximately 100–115 bpm, increasing to 140–170 bpm by 9 weeks.

Q: What is the most appropriate time for chorionic villi sampling during pregnancy?

9-11 weeks. **Explanation:** **Chorionic Villus Sampling (CVS)** is a prenatal diagnostic procedure used to detect chromosomal abnormalities and genetic disorders. The procedure involves aspirating a small sample of chorionic villi (placental tissue) either transabdominally or transcervically. **Why 9–11 weeks is correct:** The optimal window for CVS is typically between **10 and 12 weeks** of gestation (often cited as 9–11 weeks in standard textbooks like Williams Obstetrics). This timing is chosen because the chorion frondosum is sufficiently developed to provide an adequate sample, and it allows for early diagnosis and safer termination of pregnancy if an abnormality is found. **Analysis of Incorrect Options:** * **Option A & B (16–18/20 weeks):** These timeframes are appropriate for **Amniocentesis**, not CVS. Performing CVS this late offers no advantage over amniocentesis, which carries a lower risk of procedure-related pregnancy loss at this stage. * **Option D (8–10 weeks):** Performing CVS **before 9–10 weeks** is contraindicated. Early CVS is associated with an increased risk of **Limb Reduction Defects** (oromandibular-limb hypogenesis) due to vascular disruption during the procedure. **High-Yield Clinical Pearls for NEET-PG:** * **Advantage:** CVS provides results earlier than amniocentesis (which is done at 15–20 weeks). * **Disadvantage:** CVS cannot detect **Neural Tube Defects (NTDs)** because it does not measure Alpha-fetoprotein (AFP) levels in the amniotic fluid. * **Complication:** The most specific risk associated with early CVS is limb-reduction defects. * **Confined Placental Mosaicism:** This is a unique limitation of CVS where the placenta has a different genetic makeup than the fetus, potentially leading to false-positive results.

Q: Chorionic villous sampling done before 10 weeks may result in which of the following?

Oromandibular limb defects. **Explanation:** **Chorionic Villus Sampling (CVS)** is a prenatal diagnostic procedure typically performed between **10 and 13 weeks** of gestation. Performing CVS **before 10 weeks** is contraindicated due to the high risk of **Oromandibular Limb Hypogenesis Syndrome (OLHS)**. 1. **Why Option C is Correct:** The underlying mechanism is believed to be **vascular disruption**. Early instrumentation can cause placental hemorrhage and hypotension, leading to reduced perfusion in the developing fetal extremities and mandible. This results in terminal transverse limb reduction defects and oromandibular malformations. 2. **Why other options are incorrect:** * **A & B (Fetal loss and Fetomaternal hemorrhage):** While these are known complications of CVS regardless of the timing, they are not the *specific* or unique consequence of performing the procedure before 10 weeks. The risk of fetal loss is approximately 0.5–1% when performed by experienced hands during the recommended window. * **D (Insufficient material):** While the placenta is smaller earlier in pregnancy, the primary reason for delaying CVS is safety (teratogenicity), not technical failure or sample quantity. **High-Yield Facts for NEET-PG:** * **Optimal Timing:** CVS (10–13 weeks), Amniocentesis (15–20 weeks), Cordocentesis (>18 weeks). * **Early Amniocentesis (<14 weeks):** Associated with a higher risk of **Talipes Equinovarus (Clubfoot)** and fetal loss. * **CVS Advantage:** Provides earlier results than amniocentesis but cannot detect **Neural Tube Defects (NTDs)** because it does not measure Alpha-fetoprotein (AFP). * **Rh-Negative Mothers:** Must receive Anti-D immunoglobulin after CVS to prevent isoimmunization.

Q: A 22-week pregnant woman has had exposure to rubella. What is the appropriate management?

Continue the pregnancy.. The management of Rubella exposure in pregnancy depends heavily on the **gestational age** at the time of infection. ### **Explanation of the Correct Answer** The risk of **Congenital Rubella Syndrome (CRS)** is highest during the first trimester (up to 80% risk before 12 weeks). As the pregnancy progresses, the risk of fetal malformations decreases significantly. By **20 weeks of gestation**, the risk of CRS becomes negligible. Since this patient is at **22 weeks**, the risk of congenital anomalies is minimal, and there is no indication for termination of pregnancy or aggressive intervention. Therefore, the appropriate management is to **continue the pregnancy** with routine antenatal care. ### **Why Other Options are Incorrect** * **Options A, B, and D:** The MMR vaccine is a **Live Attenuated Vaccine**. Live vaccines are strictly **contraindicated during pregnancy** due to the theoretical risk of the vaccine virus crossing the placenta and infecting the fetus. MMR should only be administered in the postpartum period to non-immune women. ### **NEET-PG High-Yield Pearls** * **Critical Period:** The highest risk for CRS is during the first **12 weeks** (organogenesis). After **16–20 weeks**, the risk of major defects is nearly zero. * **Classic Triad of CRS:** 1. Cataract, 2. Sensorineural hearing loss (most common), 3. Congenital heart disease (PDA/Pulmonary artery stenosis). * **Vaccination Timing:** If a woman receives the MMR vaccine, she should be advised to avoid pregnancy for at least **4 weeks (1 month)**. * **Diagnosis:** If exposure occurs <20 weeks, maternal IgM levels should be checked. If positive, fetal infection is confirmed via amniocentesis (PCR for Rubella RNA).

Q: Prenatal diagnosis at 16 weeks of pregnancy can be performed using all of the following, except:

Fetal blood. **Explanation:** The correct answer is **Fetal blood (Option D)** because **Cordocentesis** (Percutaneous Umbilical Blood Sampling - PUBS) is typically performed only after **18 weeks** of gestation. Before this period, the umbilical vein is too small and fragile, making the procedure technically difficult and increasing the risk of pregnancy loss. **Analysis of Options:** * **Amniotic fluid (Amniocentesis):** This is the gold standard for prenatal diagnosis in the second trimester. It is ideally performed between **15–20 weeks**. Since 16 weeks falls within this window, it is a valid method. * **Maternal blood:** Non-Invasive Prenatal Testing (NIPT/Cell-free DNA) can be performed as early as **10 weeks** and remains a viable screening tool at 16 weeks. Maternal serum screening (Quadruple marker) is also ideally done between **15–18 weeks**. * **Chorionic villi (CVS):** While CVS is traditionally performed between **10–13 weeks** (first trimester), it can technically be performed later in pregnancy (late CVS) if placental localization allows, though amniocentesis is usually preferred at 16 weeks. * **Fetal blood:** As stated, the vessels are not developed enough for safe sampling at 16 weeks. **High-Yield Clinical Pearls for NEET-PG:** * **Chorionic Villus Sampling (CVS):** Best time 10–13 weeks. Earliest invasive test. Risk: Limb reduction defects if done 18 weeks. Used for rapid karyotyping, fetal infections, and managing fetal anemia (Rh isoimmunization). * **NIPT:** Most sensitive screening for Trisomy 21. Can be done from 10 weeks onwards.

Q: What is the best method for confirming pregnancy at six weeks gestation?

Ultrasound for cardiac activity. **Explanation:** The gold standard for confirming a viable intrauterine pregnancy at six weeks gestation is the visualization of **fetal cardiac activity via Transvaginal Sonography (TVS)**. At this stage, a gestational sac and yolk sac should be visible, and the presence of a flickering cardiac motion within the fetal pole (embryo) provides definitive proof of life and viability. **Analysis of Options:** * **A. Ultrasound for cardiac activity (Correct):** TVS can detect cardiac activity as early as 5.5 to 6 weeks (when the Crown-Rump Length is approximately 2–5 mm). It is the most reliable method to differentiate a viable pregnancy from a missed abortion or a blighted ovum. * **B. Doppler assessment:** While Doppler can detect fetal heart sounds, it is generally not effective or recommended until **10–12 weeks** of gestation. Using it at 6 weeks is clinically premature and technically difficult. * **C. Estimation of serum beta-hCG:** While beta-hCG confirms "biochemical" pregnancy, it cannot confirm viability, location (intrauterine vs. ectopic), or gestational age as accurately as an ultrasound at 6 weeks. * **D. Bimanual palpation:** Physical signs like Hegar’s sign or uterine enlargement are subjective and typically become reliable only after **8–10 weeks**. It cannot confirm cardiac activity. **High-Yield NEET-PG Pearls:** * **Discriminatory Zone:** The level of beta-hCG at which a gestational sac should be visible on TVS is **1,500–2,000 mIU/mL**. * **First Sign on USG:** The **Gestational Sac** is the first evidence of pregnancy (4.5–5 weeks). * **Most Accurate Dating:** Crown-Rump Length (CRL) measured in the first trimester (7–12 weeks) is the most accurate method for pregnancy dating (error margin ± 3–5 days).

Q: What is the ideal timing for detecting anencephaly?

14-16 weeks. **Explanation:** Anencephaly is a lethal neural tube defect characterized by the absence of the cranial vault and cerebral hemispheres. The diagnosis is primarily made via ultrasonography. **Why 14-16 weeks is the ideal timing:** While the precursor to anencephaly (exencephaly) can sometimes be visualized earlier, the **ideal** timing for a definitive diagnosis is **14-16 weeks**. By this stage, the ossification of the fetal skull bones (calvarium) is complete. Before 12-14 weeks, incomplete mineralization of the skull can lead to false positives or diagnostic uncertainty. At 14-16 weeks, the "Frog-eye appearance" (due to absent calvarium and prominent orbits) becomes unmistakable on ultrasound. **Analysis of Incorrect Options:** * **10-12 weeks:** Diagnosis is difficult and unreliable because skull ossification is not yet complete. The brain may still be present (exencephaly) and has not yet degenerated due to exposure to amniotic fluid. * **16-18 weeks & 18-20 weeks:** While anencephaly is easily detected at these stages (often during the routine Level II anomaly scan), it is not the "ideal" timing. Early detection (by 14-16 weeks) is preferred to allow for a safer and less psychologically traumatic medical termination of pregnancy (MTP). **High-Yield Clinical Pearls for NEET-PG:** * **USG Signs:** "Frog-eye appearance" or "Mickey Mouse sign" (in early stages). * **Biochemical Marker:** Elevated **Alpha-Fetoprotein (AFP)** in maternal serum and amniotic fluid. * **Associated Condition:** Often associated with **polyhydramnios** (due to failure of the fetus to swallow amniotic fluid). * **Prevention:** 400 mcg of Folic acid daily (pre-conceptionally); 4 mg daily if there is a previous history of NTD.

Question 1

A 25-year-old pregnant woman, at 16 weeks of gestation, presents with a positive screening test for a fetal neural tube defect. Ultrasound reveals a 3-cm neural tube defect in the thoracic spine. Which serum protein is measured in the screening test administered to the mother?

Accepted Answer

Alpha-fetoprotein

Answer

Albumin

Answer

Bilirubin

Answer

Chromogranin

Question 2

Cardiac activity of the fetus is typically seen by ultrasound by which gestational week?

Accepted Answer

6 weeks

Answer

4 weeks

Answer

5 weeks

Answer

7 weeks

Question 3

What is the most appropriate time for chorionic villi sampling during pregnancy?

Accepted Answer

9-11 weeks

Answer

16-18 weeks

Answer

16-20 weeks

Answer

8-10 weeks

Question 4

Chorionic villous sampling done before 10 weeks may result in which of the following?

Accepted Answer

Oromandibular limb defects

Answer

Fetal loss

Answer

Fetomaternal hemorrhage

Answer

Insufficient material obtained

Question 5

A 22-week pregnant woman has had exposure to rubella. What is the appropriate management?

Accepted Answer

Continue the pregnancy.

Answer

MMR vaccine should be given immediately.

Answer

MMR vaccine should be given in the 3rd trimester.

Answer

MMR vaccine should be given during labor.

Question 6

Prenatal diagnosis at 16 weeks of pregnancy can be performed using all of the following, except:

Accepted Answer

Fetal blood

Answer

Amniotic fluid

Answer

Maternal blood

Answer

Chorionic villi

Question 7

What is the best method for confirming pregnancy at six weeks gestation?

Accepted Answer

Ultrasound for cardiac activity

Answer

Doppler assessment

Answer

Estimation of serum beta-hCG

Answer

Bimanual palpation

Question 8

A 31-year-old G3P2L2 presents at 34 weeks gestation with baseline blood pressures of 100-110/60-70 mmHg. She has bilateral pedal edema. Her urine dipstick shows trace protein, and her current blood pressure is 115/75 mmHg. On physical examination, there is pitting edema of both legs without any calf tenderness. What is the best management now?

Accepted Answer

This is a normal finding of pregnancy, and no treatment is needed.

Answer

Administer furosemide to reduce the swelling.

Answer

Perform urgent venous Doppler studies to rule out deep vein thrombosis.

Answer

Admit the patient and rule out preeclampsia.

Question 9

What is the ideal timing for detecting anencephaly?

Accepted Answer

14-16 weeks

Answer

10-12 weeks

Answer

16-18 weeks

Answer

18-20 weeks

Question 10

A pregnant mother is treated with oral anticoagulant. What is the likely congenital malformation that may result in the fetus?

Accepted Answer

Chondrodysplasia punctata

Answer

Long bones limb defect

Answer

Cranial malformation

Answer

Cardiovascular malformation

Prenatal Care — MCQs

Prenatal Care — MCQs

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