Prenatal Care — MCQs
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Anti-D Rh immunoglobulin is indicated in which of the following situations?
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?
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?
The most definitive clinical sign of pregnancy is:
What is the best approach to prevent congenital anomalies in infants of diabetic mothers?
Prenatal Care Indian Medical PG Practice Questions and MCQs
Question 1: Anti-D Rh immunoglobulin is indicated in which of the following situations?
- A. Rh positive father, Rh positive mother
- B. Rh negative father, Rh positive mother
- C. Rh negative father, Rh negative mother
- D. Rh positive father, Rh negative mother (Correct Answer)
Explanation: **Explanation:** The primary objective of administering **Anti-D Rh immunoglobulin** is to prevent **Rh isoimmunization** (Rh sensitization). This condition occurs when an Rh-negative mother is exposed to Rh-positive fetal red blood cells, leading to the production of maternal antibodies that can cause Hemolytic Disease of the Fetus and Newborn (HDFN) in subsequent pregnancies. **Why Option D is Correct:** For Rh isoimmunization to occur, there must be **Rh feto-maternal incompatibility**. This is only possible if the **mother is Rh-negative** and the **father is Rh-positive**. If the father is Rh-positive, the fetus has a high probability (50-100%) of being Rh-positive. If fetal Rh-positive blood enters the maternal circulation (e.g., during delivery, miscarriage, or amniocentesis), the mother’s immune system recognizes the D-antigen as foreign and produces antibodies. Anti-D immunoglobulin neutralizes these fetal cells before sensitization occurs. **Why Other Options are Incorrect:** * **Options A & B:** If the **mother is Rh-positive**, she already possesses the D-antigen. Her immune system will not produce antibodies against it; therefore, there is no risk of isoimmunization. * **Option C:** If **both parents are Rh-negative**, the fetus will inevitably be Rh-negative. Since there is no D-antigen present in either the mother or the fetus, no immune response can be triggered. **High-Yield Clinical Pearls for NEET-PG:** * **Standard Dose:** 300 µg (1500 IU) is the standard dose, which can neutralize up to **30 ml** of fetal whole blood (or 15 ml of packed RBCs). * **Routine Timing:** In an unsensitized Rh-negative mother, Anti-D is typically given at **28 weeks** of gestation and again within **72 hours of delivery** (if the neonate is confirmed Rh-positive). * **Kleihauer-Betke Test:** Used to quantify the volume of feto-maternal hemorrhage to determine if additional doses of Anti-D are required. * **Indirect Coombs Test (ICT):** Must be **negative** in the mother before administering Anti-D; a positive ICT indicates that sensitization has already occurred, making Anti-D ineffective.
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?
- A. 2%
- B. 4% (Correct Answer)
- C. 10%
- D. 20%
Explanation: **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.
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?
- A. Triple screen test
- B. Amniocentesis (Correct Answer)
- C. Chorionic villous sampling
- D. Ultrasound (USG)
Explanation: **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.
Question 4: The most definitive clinical sign of pregnancy is:
- A. Ballottement
- B. Fetal heart sounds (Correct Answer)
- C. Braxton Hicks contractions
- D. Enlarged uterus
Explanation: ### 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 5: What is the best approach to prevent congenital anomalies in infants of diabetic mothers?
- A. Discontinue insulin and begin glyburide
- B. Switch from an oral hypoglycemic agent to insulin until 36 weeks of gestation
- C. Provide continuous insulin infusion during labor and delivery
- D. Maintain periconceptional tight control of maternal blood glucose levels (Correct Answer)
Explanation: ### Explanation **1. Why Option D is Correct:** The critical period for fetal organogenesis occurs during the first **3–8 weeks** of gestation, often before a woman realizes she is pregnant. In diabetic mothers, hyperglycemia during this window is highly teratogenic, leading to a 4–8 fold increase in major structural malformations (most commonly cardiac and neural tube defects). Therefore, the **periconceptional period** (pre-conception and early first trimester) is the most vital time for tight glycemic control to normalize the intrauterine environment and reduce the risk of congenital anomalies to near-baseline levels. **2. Why Other Options are Incorrect:** * **Option A:** Glyburide is generally not the first-line treatment in pre-gestational diabetes. Discontinuing insulin in favor of oral agents often leads to suboptimal control, increasing the risk of anomalies. * **Option B:** While switching to insulin is standard practice, limiting it "until 36 weeks" is incorrect. Tight control must be maintained throughout the entire pregnancy to prevent macrosomia and stillbirth, and specifically *before* conception to prevent anomalies. * **Option C:** Insulin infusion during labor prevents **neonatal hypoglycemia** by stabilizing maternal glucose levels at delivery; however, it has no impact on preventing congenital anomalies, which are established in the first trimester. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most Common Anomaly:** Ventricular Septal Defect (VSD) and other cardiac malformations. * **Most Specific Anomaly:** **Caudal Regression Syndrome** (Sacral agenesis) is highly characteristic of diabetic embryopathy. * **Target HbA1c:** Ideally, HbA1c should be **<6.5%** (or <6.0% if achievable without hypoglycemia) prior to conception. * **Screening:** Diabetic mothers require a **Fetal Echocardiogram** (at 18–22 weeks) in addition to a Level II anomaly scan.
Practice by Chapter
Preconception Counseling
Practice Questions
Pregnancy Diagnosis and Dating
Practice Questions
Routine Antenatal Assessments
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Maternal Physiological Changes
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Nutrition in Pregnancy
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Screening Tests in Pregnancy
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Fetal Growth Assessment
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High-Risk Pregnancy Identification
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Antenatal Complications Management
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Psychosocial Aspects of Pregnancy
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