Prenatal Care Practice Questions

Q: A patient presents for her first initial OB visit, with her last menstrual period approximately 8 weeks ago. She is unsure of her dates due to a history of irregular menses. Which of the following is the most accurate method for dating this pregnancy?

Crown-rump length on vaginal ultrasound. **Explanation:** The most accurate method for dating a pregnancy, especially in the first trimester, is the **Crown-Rump Length (CRL)** measured via ultrasound. **1. Why Option C is Correct:** In early pregnancy, fetal growth is highly uniform across all pregnancies because it is minimally influenced by external factors (like genetics or placental insufficiency) at this stage. A transvaginal ultrasound (TVUS) can measure the CRL with a margin of error of only **+/- 3 to 5 days**. According to ACOG guidelines, if there is a discrepancy between the Last Menstrual Period (LMP) and the CRL, the ultrasound dating is preferred, particularly in patients with irregular menses where the date of ovulation is uncertain. **2. Why Other Options are Incorrect:** * **Option A:** Uterine size on pelvic exam is subjective and can be confounded by factors such as maternal obesity, uterine fibroids, a retroverted uterus, or multiple gestations. It is far less precise than imaging. * **Option B & D:** While serum hCG and progesterone levels are useful for confirming pregnancy viability or diagnosing an ectopic pregnancy, they cannot be used for dating. hCG levels have a massive "normal" range at any given gestational age, making them unreliable for determining the exact week of pregnancy. **3. NEET-PG Clinical Pearls:** * **First Trimester (up to 13+6 weeks):** CRL is the "Gold Standard" for dating. * **Second Trimester (14–22 weeks):** A composite of Biparietal Diameter (BPD), Head Circumference (HC), Abdominal Circumference (AC), and Femur Length (FL) is used (Accuracy: +/- 7–10 days). * **Third Trimester:** Accuracy drops significantly (+/- 21 days); dating should not be changed based on a third-trimester scan if an earlier scan is available. * **Rule of Thumb:** The earlier the ultrasound, the more accurate the dating.

Q: A woman has previously had 2 anencephalic babies. What is her risk of having a third baby with anencephaly?

10%. Neural Tube Defects (NTDs), such as anencephaly and spina bifida, follow a **multifactorial inheritance** pattern. This means they result from a complex interaction between multiple genes and environmental factors (like folic acid deficiency). **Explanation of the Correct Answer:** In multifactorial inheritance, the recurrence risk increases with the number of previously affected siblings. * After **one** child with an NTD, the recurrence risk is approximately **2-5%**. * After **two** children with an NTD, the risk significantly increases to approximately **10%**. This 10% risk represents a high-risk category, necessitating aggressive preconception counseling and high-dose folic acid supplementation. **Analysis of Incorrect Options:** * **0%:** Incorrect, as NTDs have a strong genetic predisposition; a history of affected offspring significantly elevates future risk. * **25%:** This risk is characteristic of **Autosomal Recessive** disorders (e.g., Thalassemia). While some rare syndromes involving NTDs (like Meckel-Gruber syndrome) follow this pattern, isolated anencephaly does not. * **50%:** This risk is characteristic of **Autosomal Dominant** disorders (if one parent is affected) or X-linked carriers. **High-Yield Clinical Pearls for NEET-PG:** * **Prevention:** To prevent recurrence in high-risk women (those with a previous affected child), **4 mg (4000 µg)** of Folic Acid is recommended daily, starting 1–3 months before conception. * **Low-risk prophylaxis:** For women with no prior history, the standard dose is **0.4 mg (400 µg)**. * **Screening:** Maternal Serum Alpha-Fetoprotein (**MSAFP**) is elevated in open NTDs like anencephaly. * **Diagnosis:** Ultrasound is the gold standard; anencephaly can be detected as early as 11–14 weeks (the "frog-eye" appearance).

Q: At what stage of pregnancy is quickening typically felt?

Fifth month. **Explanation:** **Quickening** refers to the first perception of active fetal movements by the mother. It is a subjective clinical sign used to assess fetal well-being and estimate gestational age. 1. **Why Option B is correct:** In clinical practice, quickening typically occurs between **18 to 20 weeks** of gestation in primigravida (first-time mothers) and slightly earlier, around **16 to 18 weeks**, in multigravida (due to prior experience). Since the fifth month of pregnancy spans from 17 to 20 weeks, it is the most accurate timeframe for the onset of these movements. 2. **Why other options are incorrect:** * **Option A (Second month):** At 8 weeks, the embryo is just becoming a fetus; movements are microscopic and cannot be felt. * **Option C & D (10 & 12 weeks):** While fetal movements can be visualized on ultrasound as early as 8–10 weeks, the fetus is too small and the muscular contractions too weak for the mother to perceive them through the uterine wall and abdominal layers at this stage. **High-Yield Clinical Pearls for NEET-PG:** * **Primigravida:** Quickening at **18–20 weeks**. * **Multigravida:** Quickening at **16–18 weeks**. * **Significance:** Quickening is a "presumptive" sign of pregnancy. It helps in calculating the Expected Date of Delivery (EDD) if the Last Menstrual Period (LMP) is unknown (Add 22 weeks for primigravida; 24 weeks for multigravida). * **Differential Diagnosis:** Intestinal peristalsis or gas bubbles can sometimes be mistaken for quickening (pseudocyesis).

Q: What is the recommended dose of anti-D immunoglobulin for antenatal prophylaxis in Rh-negative, non-immunized females?

1500 IU at 28 weeks. **Explanation:** The primary goal of antenatal prophylaxis in Rh-negative, non-immunized (indirect Coombs test negative) women is to prevent **Rh isoimmunization** caused by silent feto-maternal hemorrhages that typically occur in the third trimester. **Why Option B is Correct:** Current international guidelines (RCOG and NICE) and standard obstetric practice recommend a dose of **1500 IU (300 mcg)** of anti-D immunoglobulin. This is ideally administered at **28 weeks of gestation** because the risk of sensitization increases significantly after this period, and the half-life of the immunoglobulin ensures protection until delivery. This single-dose regimen is highly effective in reducing the incidence of maternal sensitization from ~1.5% to 0.2%. **Analysis of Incorrect Options:** * **Option A (1000 IU):** This is an insufficient dose for standard single-dose prophylaxis. While some protocols use two doses of 500 IU (at 28 and 34 weeks), 1000 IU as a single dose is not the standard recommendation. * **Option C (500 IU):** This dose is typically reserved for first-trimester sensitizing events (e.g., miscarriage or ectopic pregnancy before 12-20 weeks) but is inadequate for routine third-trimester prophylaxis. * **Option D (32 weeks):** Waiting until 32 weeks leaves a "window of vulnerability" between 28 and 32 weeks where sensitization could occur. **High-Yield Clinical Pearls for NEET-PG:** * **Standard Dose:** 300 mcg = 1500 IU (Conversion: 1 mcg = 5 IU). * **Postpartum Dose:** 1500 IU must be given within **72 hours** of delivery if the newborn is Rh-positive. * **Kleihauer-Betke Test:** Used to quantify feto-maternal hemorrhage to determine if additional anti-D doses are required (10 mcg covers 0.5 ml of fetal red cells or 1 ml of whole blood). * **Indirect Coombs Test (ICT):** Must be negative before administering prophylaxis; if ICT is positive, the woman is already sensitized, and anti-D is of no use.

Q: What is the recommended treatment for Chlamydia infection during pregnancy?

Azithromycin. **Explanation:** The primary goal of treating Chlamydia trachomatis during pregnancy is to prevent maternal complications (pelvic inflammatory disease, preterm labor) and neonatal transmission (ophthalmia neonatorum, pneumonia). **Why Azithromycin is correct:** **Azithromycin (1g orally in a single dose)** is the first-line treatment recommended by the WHO and CDC for chlamydial infection in pregnancy. It is highly effective, has a high safety profile (Category B), and the single-dose regimen ensures 100% compliance, which is crucial in prenatal care. Amoxicillin is considered an alternative if Azithromycin is contraindicated. **Why other options are incorrect:** * **Doxycycline and Tetracycline:** These are the first-line treatments in non-pregnant adults. However, they are **contraindicated in pregnancy** (Category D) because they cross the placenta and can cause permanent yellow-brown discoloration of the deciduous teeth and inhibit fetal bone growth. * **Penicillin:** While safe in pregnancy, Penicillin is ineffective against *Chlamydia trachomatis* because Chlamydia is an obligate intracellular bacterium that lacks a typical peptidoglycan cell wall, making it resistant to beta-lactam antibiotics. **Clinical Pearls for NEET-PG:** * **Screening:** All pregnant women should be screened for Chlamydia at the first prenatal visit. * **Test of Cure (TOC):** Unlike in non-pregnant patients, a TOC (via Nucleic Acid Amplification Test - NAAT) is mandatory **3–4 weeks after treatment** in pregnancy to ensure eradication. * **Partner Treatment:** To prevent reinfection, the partner must be treated simultaneously (Expedited Partner Therapy). * **Neonatal Impact:** Chlamydial conjunctivitis typically appears 5–14 days after birth (later than Gonococcal conjunctivitis, which appears in 2–5 days).

Q: Elevated maternal serum alpha-fetoprotein (AFP) is seen in which of the following conditions?

Trisomy 21 (Down syndrome). **Explanation:** The question asks for conditions associated with **elevated** maternal serum alpha-fetoprotein (MSAFP). However, there is a discrepancy in the provided key: **Trisomy 21 (Down syndrome) is actually associated with LOW MSAFP levels.** **1. Understanding the Correct Answer (Correction):** In clinical practice and for NEET-PG, it is crucial to remember that **Trisomy 21** is characterized by a "Low AFP, Low Estriol, and High hCG" pattern in the triple screen. If the question intended to identify a condition with *elevated* AFP, options A, C, and D would all be correct. If the question asks which condition is associated with *low* AFP, then **Option B (Trisomy 21)** is the only correct answer. **2. Analysis of Options (Causes of Elevated AFP):** * **Open Neural Tube Defects (C):** This is the most common cause of pathological elevation. Failure of neural tube closure allows AFP to leak from the fetal cerebrospinal fluid into the amniotic fluid and maternal circulation. * **Multiple Pregnancy (A):** More than one fetus produces a higher cumulative volume of AFP, leading to elevated maternal levels. * **Intrauterine Fetal Demise (D):** Fetal death leads to a breakdown of the fetal-maternal barrier, causing a massive release of AFP into the maternal blood. * **Other causes:** Omphalocele, Gastroschisis, and Renal anomalies (Finnish-type nephrosis). **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of elevated MSAFP:** Under-estimation of gestational age (wrong dates). * **Down Syndrome Marker Pattern:** Low AFP, Low uE3 (Estriol), High hCG, and High Inhibin A ("HI" for High = hCG and Inhibin). * **Trisomy 18 (Edwards Syndrome):** All markers (AFP, hCG, uE3) are **decreased**. * **Timing:** MSAFP screening is ideally performed between **15–20 weeks** of gestation.

Q: Increased nuchal fold thickness is a feature of which condition?

Down's syndrome. **Explanation:** **Down’s Syndrome (Trisomy 21)** is the most common chromosomal disorder and is frequently associated with specific ultrasound markers during pregnancy. **Increased nuchal fold thickness** (measured in the second trimester, typically between 15–20 weeks) is a highly sensitive soft marker for Down’s syndrome. It is defined as a measurement of **≥6 mm**. This is distinct from *nuchal translucency*, which is measured in the first trimester (11–13.6 weeks). The increased thickness is thought to result from lymphatic obstruction or delayed development of the lymphatic system in the cervical region. **Analysis of Incorrect Options:** * **Paul–Bunnel Syndrome:** This is not a congenital or chromosomal disorder; the Paul–Bunnell test is a heterophile antibody test used to diagnose **Infectious Mononucleosis** (EBV). * **De–pan Syndrome:** This is not a recognized clinical entity in standard pediatric or genetic literature. It may be a distractor or a misspelling of other rare syndromes, but it is not associated with nuchal thickening. * **Cri–du-chat Syndrome (5p deletion):** While this syndrome presents with microcephaly, a cat-like cry, and epicanthal folds, it is not classically associated with increased nuchal fold thickness as a primary diagnostic marker. **High-Yield Clinical Pearls for NEET-PG:** * **Nuchal Translucency (NT):** Measured in the 1st trimester; >3 mm is considered abnormal and suggests Trisomy 21, 18, 13, or Turner syndrome. * **Other USG markers for Down’s:** Hypoplastic/absent nasal bone, echogenic intracardiac focus, "double bubble" sign (duodenal atresia), and short femur/humerus. * **Quadruple Marker Test:** In Down’s syndrome, **AFP and Estriol are LOW**, while **hCG and Inhibin-A are HIGH** (Mnemonic: **HI**gh = **H**cg & **I**nhibin).

Question 1

A patient presents for her first initial OB visit, with her last menstrual period approximately 8 weeks ago. She is unsure of her dates due to a history of irregular menses. Which of the following is the most accurate method for dating this pregnancy?

Accepted Answer

Crown-rump length on vaginal ultrasound

Answer

Determination of uterine size on pelvic examination

Answer

Quantitative serum hCG levels

Answer

Determination of progesterone levels along with serum hCG levels

Question 2

A 30-year-old woman with a previous history of stillbirth at 24 weeks of gestation is now at 30 weeks of gestation. What is her obstetric score?

Accepted Answer

G2P1L0

Answer

G1Ab1

Answer

G2Ab1

Answer

G2P2L0

Question 3

A woman has previously had 2 anencephalic babies. What is her risk of having a third baby with anencephaly?

Accepted Answer

10%

Answer

0%

Answer

25%

Answer

50%

Question 4

At what stage of pregnancy is quickening typically felt?

Accepted Answer

Fifth month

Answer

Second month

Answer

10 weeks

Answer

12 weeks

Question 5

What is the recommended dose of anti-D immunoglobulin for antenatal prophylaxis in Rh-negative, non-immunized females?

Accepted Answer

1500 IU at 28 weeks

Answer

1000 IU at 28 weeks

Answer

500 IU at 28 weeks

Answer

1500 IU at 32 weeks

Question 6

What is the recommended treatment for Chlamydia infection during pregnancy?

Accepted Answer

Azithromycin

Answer

Doxycycline

Answer

Tetracycline

Answer

Penicillin

Question 7

Elevated maternal serum alpha-fetoprotein (AFP) is seen in which of the following conditions?

Accepted Answer

Trisomy 21 (Down syndrome)

Answer

Multiple pregnancy

Answer

Open neural tube defect

Answer

Intrauterine fetal demise (IUD)

Question 8

The triple test for Down syndrome screening includes which of the following biochemical markers?

Accepted Answer

Maternal Alpha-fetoprotein (AFP), Human Chorionic Gonadotropin (HCG), and Estriol

Answer

Maternal Alpha-fetoprotein (AFP), Pregnancy-Associated Plasma Protein-A (PAPPA), and Human Chorionic Gonadotropin (HCG)

Answer

Maternal Alpha-fetoprotein (AFP), Pregnancy-Associated Plasma Protein-A (PAPPA), and Estriol

Answer

Thyroid-Stimulating Hormone (TSH), Human Chorionic Gonadotropin (HCG), and Estriol

Question 9

A 38-year-old G3 P2 presents with 10 weeks of amenorrhea. Her serum β-hCG level is 25,000 mIU/mL, and her internal cervical os is closed. On USG, an anechoic intrauterine area measures 40mm, and the adnexa are normal. What is the diagnosis?

Accepted Answer

Missed abortion

Answer

Complete abortion

Answer

Threatened abortion

Answer

Complete Hydatidiform mole

Question 10

Increased nuchal fold thickness is a feature of which condition?

Accepted Answer

Down's syndrome

Answer

Paul–Bunnel syndrome

Answer

De–pan syndrome

Answer

Cri–du chat syndrome

Prenatal Care — MCQs

Prenatal Care — MCQs

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