Prenatal Care Practice Questions

Q: What is the approximate recurrence risk for neural tube defects (NTDs) in a subsequent pregnancy, given that the first baby was born with an NTD?

4%. **Explanation:** Neural tube defects (NTDs) follow a **multifactorial inheritance** pattern, meaning they result from a combination of genetic predisposition and environmental factors (most notably folic acid deficiency). **1. Why 4% is correct:** In the general population, the incidence of NTDs is approximately 0.1–0.2% (1 in 1,000). However, once a couple has one child with an NTD (anencephaly, spina bifida, or encephalocele), the risk of recurrence in a subsequent pregnancy increases significantly to approximately **3–5%** (standardized as **4%** for examination purposes). If two previous siblings are affected, the risk rises further to about 10%. **2. Why the other options are incorrect:** * **A (2%):** This underestimates the risk. While recurrence risks vary by geography, 3–5% is the globally accepted range for a single prior affected pregnancy. * **C (10%):** This is the approximate recurrence risk only after **two** previously affected siblings. * **D (20%):** This risk is too high for multifactorial inheritance and would be more characteristic of a high-penetrance autosomal dominant condition. **High-Yield Clinical Pearls for NEET-PG:** * **Prevention:** For the general population, the recommended dose of Folic Acid is **400 mcg (0.4 mg)/day** starting 1 month prior to conception. * **Secondary Prevention (High Risk):** For women with a **previous child with NTD**, the dose is increased to **4 mg/day** (10 times the standard dose). * **Screening:** Maternal Serum Alpha-Fetoprotein (MSAFP) is elevated in open NTDs. The best time for screening is **15–20 weeks** (ideal: 16–18 weeks). * **Diagnosis:** Targeted Level II Ultrasound is the gold standard for detecting structural defects.

Q: What is the investigation of choice in a pregnant lady at 16 weeks of gestation with a history of delivering a baby with Down syndrome?

Amniocentesis. **Explanation:** The core concept here is distinguishing between **screening** and **diagnostic** tests in a high-risk pregnancy. A history of a prior child with Down syndrome significantly increases the risk of recurrence, necessitating a definitive diagnosis rather than a risk assessment. 1. **Why Amniocentesis is correct:** Amniocentesis is a **diagnostic test** that involves karyotyping fetal cells obtained from amniotic fluid. It is ideally performed between **15–20 weeks** of gestation. Since the patient is at 16 weeks, amniocentesis is the investigation of choice to provide a definitive chromosomal analysis with a high degree of accuracy (>99%). 2. **Why other options are incorrect:** * **Triple screen test:** This is a screening tool (measuring AFP, hCG, and uE3). In a patient with a high-risk history, screening is insufficient; a diagnostic test is required to confirm or rule out the condition. * **Chorionic Villous Sampling (CVS):** While CVS is also a diagnostic test, it is typically performed between **10–13 weeks**. At 16 weeks, the window for CVS has passed, making amniocentesis the appropriate choice. * **Ultrasound (USG):** USG can identify "soft markers" (like nuchal fold thickness) but cannot provide a definitive genetic diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **Timing is Key:** CVS (10–13 weeks), Amniocentesis (15–20 weeks), Cordocentesis (>20 weeks). * **Most common chromosomal abnormality** associated with increased maternal age or prior history is Trisomy 21 (Down syndrome). * **Amniocentesis Risk:** The procedure-related risk of miscarriage is approximately 0.5% (1 in 200). * **Quadruple Screen:** Includes Triple Screen + Inhibin A; it is the preferred screening test in the second trimester if invasive testing is declined.

Q: The most definitive clinical sign of pregnancy is:

Fetal heart sounds. ### Explanation In Obstetrics, signs of pregnancy are categorized into **Presumptive, Probable, and Positive (Definitive)** signs. **1. Why Fetal Heart Sounds (FHS) is correct:** Fetal heart sounds are a **Positive sign** of pregnancy. Positive signs are those that can only be attributed to the presence of a fetus and are considered 100% diagnostic. Other positive signs include the visualization of the fetus on ultrasound and the perception of active fetal movements by an examiner. FHS can be heard via Doppler as early as 10–12 weeks and via Pinard stethoscope by 18–20 weeks. **2. Why the other options are incorrect:** * **Ballottement (A):** This is a **Probable sign**. While it suggests a floating body in the uterus, it can be mimicked by a large uterine fibroid or an ovarian cyst with ascites. * **Braxton Hicks contractions (C):** These are **Probable signs**. They are painless, irregular uterine contractions that can also occur in conditions like hematometra or soft uterine fibroids. * **Enlarged uterus (D):** This is a **Probable sign**. Uterine enlargement can be caused by pelvic tumors (fibroids), molar pregnancy, or adenomyosis, and is therefore not definitive. **Clinical Pearls for NEET-PG:** * **Presumptive signs:** Subjective symptoms felt by the mother (e.g., Amenorrhea, morning sickness, quickening, breast changes). * **Probable signs:** Objective signs noted by the examiner (e.g., Hegar’s sign, Goodell’s sign, Chadwick’s sign, positive urine hCG). * **Definitive/Positive signs:** Fetal heart sounds, fetal parts palpation (by examiner), and ultrasound evidence. * **High-yield:** The earliest definitive sign of pregnancy on ultrasound is the **Gestational Sac** (at 4.5–5 weeks).

Question 1

Anti-D Rh immunoglobulin is indicated in which of the following situations?

Accepted Answer

Rh positive father, Rh negative mother

Answer

Rh positive father, Rh positive mother

Answer

Rh negative father, Rh positive mother

Answer

Rh negative father, Rh negative mother

Question 2

What is the approximate recurrence risk for neural tube defects (NTDs) in a subsequent pregnancy, given that the first baby was born with an NTD?

Accepted Answer

4%

Answer

2%

Answer

10%

Answer

20%

Question 3

What is the investigation of choice in a pregnant lady at 16 weeks of gestation with a history of delivering a baby with Down syndrome?

Accepted Answer

Amniocentesis

Answer

Triple screen test

Answer

Chorionic villous sampling

Answer

Ultrasound (USG)

Question 4

The most definitive clinical sign of pregnancy is:

Accepted Answer

Fetal heart sounds

Answer

Ballottement

Answer

Braxton Hicks contractions

Answer

Enlarged uterus

Question 5

What is the best approach to prevent congenital anomalies in infants of diabetic mothers?

Accepted Answer

Maintain periconceptional tight control of maternal blood glucose levels

Answer

Discontinue insulin and begin glyburide

Answer

Switch from an oral hypoglycemic agent to insulin until 36 weeks of gestation

Answer

Provide continuous insulin infusion during labor and delivery

Prenatal Care — MCQs

Prenatal Care — MCQs

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