Prenatal Care Practice Questions

Q: Estimation of fetal maturity by biparietal diameter measurement is accurate to within + or -:

3-7 days. **Explanation:** The estimation of gestational age (GA) via ultrasound relies on different biometric parameters depending on the trimester. The **Biparietal Diameter (BPD)** is most accurate when measured between **12 and 20 weeks** of gestation. During this window, fetal growth is rapid and biological variation is minimal, allowing for an accuracy of **± 3 to 7 days**. * **Why Option A is correct:** In the early second trimester (specifically 14–20 weeks), the BPD is the standard parameter for dating. The predictive value is highest here because the brain growth is consistent across fetuses. As pregnancy advances, individual genetic potential and environmental factors (like IUGR or macrosomia) increase variability. * **Why Options B, C, and D are incorrect:** These ranges (7–20 days) represent the decreasing accuracy of BPD in the later stages of pregnancy. By the third trimester (after 26–30 weeks), the accuracy of BPD drops significantly to ± 2 to 3 weeks due to variations in fetal head shape (dolichocephaly or brachycephaly) and growth rates. **High-Yield Clinical Pearls for NEET-PG:** 1. **Best Overall Parameter:** Crown-Rump Length (CRL) in the first trimester (7–12 weeks) is the most accurate method for dating, with an accuracy of **± 3 to 5 days**. 2. **BPD Landmarks:** To ensure accuracy, BPD must be measured at the level of the **thalami** and **cavum septum pellucidum**. 3. **Transcerebellar Diameter (TCD):** This is the only parameter that remains reliable even in cases of IUGR, as the cerebellum is "spared" from growth restriction. 4. **Rule of Thumb:** The later the ultrasound is performed, the less accurate it is for dating the pregnancy.

Q: Air travel in pregnancy is generally permitted up to which gestational age?

36 weeks. **Explanation:** Air travel is generally considered safe for healthy pregnant women. According to guidelines from the **ACOG (American College of Obstetricians and Gynecologists)** and **RCOG**, the most common cutoff for domestic air travel in an uncomplicated singleton pregnancy is **36 weeks**. 1. **Why 36 weeks is correct:** The primary concern with late-term air travel is not the altitude or pressure, but the risk of **spontaneous labor** or rupture of membranes occurring while in flight, away from specialized obstetric care. By 36 weeks, the risk of labor increases significantly. For international flights, some airlines may have stricter cutoffs (often 32–35 weeks). 2. **Why other options are incorrect:** * **28 weeks:** This is often the threshold where airlines require a "Fit to Fly" certificate from a doctor, but it is not the limit for travel. * **32 weeks:** This is the recommended cutoff for **uncomplicated multiple pregnancies** (e.g., twins) due to the higher risk of preterm labor. * **40 weeks:** Traveling at term is contraindicated as labor is imminent, and the environment of a commercial aircraft is unequipped for delivery or neonatal emergencies. **High-Yield Clinical Pearls for NEET-PG:** * **Best time to travel:** The **second trimester** (14–28 weeks) is the safest period because the risks of miscarriage and preterm labor are lowest, and morning sickness has usually subsided. * **DVT Prophylaxis:** Pregnancy is a hypercoagulable state. To prevent Deep Vein Thrombosis (DVT) during long flights, patients should be advised to wear **compression stockings**, stay hydrated, and perform frequent calf exercises or walk every hour. * **Contraindications:** Air travel should be avoided in women with severe anemia, sickle cell disease (risk of crisis due to low partial pressure of oxygen), or obstetric complications like placenta previa or preeclampsia.

Q: At what gestational age is the weight of the placenta and fetus approximately equal?

17 weeks. **Explanation:** The relationship between fetal weight and placental weight changes dynamically throughout pregnancy. This is a high-yield concept in obstetric physiology, reflecting the shifting metabolic demands of the developing fetus. **1. Why 17 weeks is correct:** In the early second trimester, the placenta grows rapidly to establish the nutritional infrastructure required for the fetus. At approximately **17 weeks of gestation**, the growth curves of the fetus and the placenta intersect, and their weights are **nearly equal** (roughly 150–180 grams each). Prior to this point, the placenta is actually heavier than the fetus; after this point, fetal weight gain accelerates significantly, eventually far surpassing the placental weight. **2. Analysis of incorrect options:** * **14 & 15 weeks:** At these stages, the **placenta is heavier than the fetus**. The placenta must develop its vascular architecture before it can support rapid fetal mass accumulation. * **21 weeks:** By this stage, the fetus has entered a period of rapid growth. The fetus is now significantly heavier than the placenta. By term (40 weeks), the ratio of fetal weight to placental weight is approximately **6:1**. **3. High-Yield Clinical Pearls for NEET-PG:** * **Fetal-Placental Weight Ratio:** At term, the average placenta weighs about 500g, while the fetus weighs about 3000–3500g. * **Placental Growth:** The placenta continues to grow in thickness and circumference until near term, but its relative efficiency increases to meet fetal demands. * **Clinical Significance:** An abnormally large placenta (Placentomegaly) relative to fetal weight is seen in conditions like maternal diabetes, fetal hydrops, and syphilis. Conversely, a small placenta is associated with IUGR and preeclampsia.

Q: Which of the following supplements is recommended for a pregnant patient receiving antiepileptic drugs to decrease the risk of neural tube defects in the offspring?

Folic acid. **Explanation:** **1. Why Folic Acid is Correct:** Neural Tube Defects (NTDs) occur due to the failure of the neural tube to close during the first 28 days of gestation. Antiepileptic drugs (AEDs), particularly **Valproate, Carbamazepine, and Phenytoin**, interfere with folate metabolism (antagonism), significantly increasing the risk of NTDs. Supplementation with Folic acid before conception and during the first trimester is the standard of care to mitigate this risk. * **High-Yield Note:** While the standard dose for low-risk pregnancies is 400 mcg (0.4 mg), women on AEDs are considered **high-risk** and require a higher dose of **4 mg (4000 mcg)** daily, starting at least one month prior to conception. **2. Why Other Options are Incorrect:** * **Vitamin A:** Excessive intake (Retinoids) is actually **teratogenic**, leading to craniofacial, cardiac, and CNS defects (Retinoic acid embryopathy). It is not used to prevent NTDs. * **Vitamin E:** This is an antioxidant. While it has been studied for pre-eclampsia prevention, it has no proven role in preventing NTDs or counteracting AED-induced teratogenicity. * **Pyridoxine (Vitamin B6):** Primarily used in pregnancy to treat **Nausea and Vomiting of Pregnancy (NVP)** or to prevent peripheral neuropathy in patients taking Isoniazid. It does not prevent NTDs. **Clinical Pearls for NEET-PG:** * **Best time to start:** Pre-conceptionally (ideally 3 months before). * **Valproate:** Carries the highest risk of NTDs (specifically spina bifida) and cognitive impairment. * **Vitamin K:** Some guidelines recommend Vitamin K supplementation (10 mg/day) in the last month of pregnancy for women on enzyme-inducing AEDs (like Phenobarbital) to prevent neonatal hemorrhagic disease, though Folic acid remains the priority for NTDs.

Q: What is the commonest chromosomal anomaly leading to spontaneous abortions?

Trisomy 16. **Explanation:** Chromosomal anomalies are the most common cause of first-trimester spontaneous abortions, accounting for approximately 50–60% of cases. Among these, **Autosomal Trisomies** are the most frequent category (about 50% of all anomalies). **Why Trisomy 16 is correct:** While Trisomy 21 is the most common trisomy found in live births, **Trisomy 16** is the most common trisomy identified in spontaneous miscarriages. It is considered lethal and is virtually never seen in live-born infants. It accounts for approximately one-third of all trisomies found in abortuses. **Analysis of Incorrect Options:** * **Trisomy 21 (Option B):** This is the most common autosomal trisomy in **live births** (Down Syndrome). While it can cause miscarriage, it is less frequent than Trisomy 16 in early pregnancy loss. * **Tetraploidy (Option C):** This is a polyploidy (92 chromosomes). While it leads to early pregnancy loss, it is much rarer than aneuploidies like trisomy. * **Turner’s Syndrome (Option D):** Monosomy X (45,X) is the **single most common specific chromosomal abnormality** found in spontaneous abortions (accounting for ~20% of cases). However, as a group, **Trisomies** are more common than Monosomy X. If the question asks for the most common *trisomy* or the most common *anomaly* (where trisomies are grouped), Trisomy 16 is the leading specific trisomy. **NEET-PG High-Yield Pearls:** * **Most common cause of spontaneous abortion:** Chromosomal anomalies. * **Most common group of anomalies:** Autosomal Trisomies. * **Most common specific Trisomy:** Trisomy 16. * **Most common single chromosomal anomaly:** Monosomy X (45,X / Turner’s). * **Most common cause of second-trimester abortion:** Maternal factors (e.g., Cervical incompetence, uterine anomalies).

Q: What is the most accurate method for estimating gestational age using ultrasonography?

Crown-rump length. **Explanation:** The **Crown-Rump Length (CRL)** is the most accurate parameter for estimating gestational age (GA) in the first trimester (specifically between 7 and 13 weeks). During this period, fetal growth is rapid and biological variation is minimal because growth is largely unaffected by external factors like placental insufficiency or genetic growth potential. The margin of error for CRL is only **±3 to 5 days**. **Analysis of Options:** * **Crown-Rump Length (CRL):** Correct. It is the gold standard for dating. Once the CRL exceeds 84 mm (approx. 14 weeks), its accuracy decreases, and second-trimester parameters must be used. * **Biparietal Diameter (BPD):** This is the most accurate parameter in the **second trimester** (up to 20 weeks), with an error margin of ±7 to 10 days. However, it is less accurate than CRL. * **Head Circumference (HC):** While a reliable predictor of GA in the second trimester and less affected by head shape (dolichocephaly/brachycephaly) than BPD, it still lacks the precision of first-trimester CRL. * **Abdominal Circumference (AC):** This is the **least accurate** parameter for dating as it is highly sensitive to fetal nutrition and growth restriction (IUGR). Its primary role is assessing fetal weight and growth rather than GA. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest Sign of Pregnancy on USG:** Gestational Sac (seen at ~4.5–5 weeks). * **First Fetal Structure Visualized:** Yolk Sac (seen at ~5 weeks; confirms intrauterine pregnancy). * **Rule of Thumb:** If there is a discrepancy between LMP and USG dating, the **earliest ultrasound** (CRL) is always considered the most reliable for establishing the EDD. * **Mean Sac Diameter (MSD):** Used if the embryo is not yet visible; however, CRL is superior once the fetal pole appears.

Q: Maximum cardiac output in pregnancy occurs at which gestational age?

28 weeks. **Explanation:** The correct answer is **28 weeks**. Cardiac output (CO) begins to increase as early as 5 weeks of gestation due to a combination of increased stroke volume and heart rate. It rises progressively throughout the second trimester, reaching its peak between **28 and 32 weeks** of gestation. At this point, the cardiac output is approximately 30–50% higher than in the non-pregnant state. This increase is a physiological adaptation to meet the metabolic demands of the growing fetus and the placenta. **Analysis of Options:** * **A, B, and C (20, 24, and 26 weeks):** While cardiac output is steadily increasing during these weeks, it has not yet reached its maximum plateau. These options represent the "rising phase" of the hemodynamic curve. * **D (28 weeks):** This marks the beginning of the peak window (28–32 weeks). In the context of NEET-PG, if a single value is required, 28 weeks is the traditionally accepted milestone for the maximum increase in resting cardiac output. **High-Yield Clinical Pearls for NEET-PG:** 1. **The "Real" Maximum:** While 28–32 weeks is the peak during *gestation*, the absolute maximum cardiac output occurs **immediately postpartum** (due to "autotransfusion" from the contracted uterus and relief of IVC compression). 2. **Labor:** Cardiac output increases further during labor (by ~40% over late pregnancy levels) due to pain, anxiety, and uterine contractions. 3. **Clinical Significance:** Patients with underlying heart disease (e.g., Mitral Stenosis) are at the highest risk of **heart failure** during two specific periods: at **28–32 weeks** (peak volume) and **immediately after delivery**. 4. **Positioning:** In late pregnancy, cardiac output is lower in the supine position due to **Aortocaval compression**; it is highest in the left lateral recumbent position.

Question 1

Estimation of fetal maturity by biparietal diameter measurement is accurate to within + or -:

Accepted Answer

3-7 days

Answer

7-10 days

Answer

10-15 days

Answer

14-20 days

Question 2

Which of the following statements regarding cell-free DNA is FALSE?

Accepted Answer

It is an invasive technique for prenatal diagnosis of certain genetic diseases.

Answer

It is detected in maternal blood.

Answer

Prenatal diagnosis of Down's syndrome can be made using it.

Answer

It is used for liquid biopsy.

Question 3

Air travel in pregnancy is generally permitted up to which gestational age?

Accepted Answer

36 weeks

Answer

28 weeks

Answer

32 weeks

Answer

40 weeks

Question 4

At what gestational age is the weight of the placenta and fetus approximately equal?

Accepted Answer

17 weeks

Answer

14 weeks

Answer

15 weeks

Answer

21 weeks

Question 5

A 32-year-old mother, who has previously had a child with Down syndrome, is now 9 weeks pregnant and wishes to avoid having another child with Down syndrome. As her physician, what would you advise?

Accepted Answer

Chorionic villous sampling at this stage can confirm the presence or absence of Down syndrome.

Answer

Ultrasound at this stage can confirm the presence or absence of Down syndrome.

Answer

The triple test or maternal AFP screening at this stage can confirm the presence or absence of Down syndrome.

Answer

No intervention is necessary as the risk is minimal because her age is less than 35 years.

Question 6

Which of the following supplements is recommended for a pregnant patient receiving antiepileptic drugs to decrease the risk of neural tube defects in the offspring?

Accepted Answer

Folic acid

Answer

Vitamin A

Answer

Vitamin E

Answer

Pyridoxine

Question 7

A 25-year-old primigravida at 25 weeks of gestation presents for an antenatal check-up. She has a history of genital herpes infection for 5 years, usually asymptomatic with 3 flares in the past 5 years. She is concerned about exposing her unborn child to the infection. What is the most appropriate counsel to offer this patient?

Accepted Answer

Perform elective lower segment cesarean section (LSCS) only if the mother has active genital herpes at the time of delivery.

Answer

Administer one dose of acyclovir if she has active genital herpes at the time of delivery.

Answer

Administer prophylaxis with acyclovir from 25 weeks gestation until delivery, irrespective of active herpes lesions.

Answer

Perform elective lower segment cesarean section (LSCS) even if the mother is asymptomatic at the time of delivery.

Question 8

What is the commonest chromosomal anomaly leading to spontaneous abortions?

Accepted Answer

Trisomy 16

Answer

Trisomy 21

Answer

Tetraploidy

Answer

Turner's syndrome

Question 9

What is the most accurate method for estimating gestational age using ultrasonography?

Accepted Answer

Crown-rump length

Answer

Head circumference

Answer

Abdominal circumference

Answer

Biparietal diameter

Question 10

Maximum cardiac output in pregnancy occurs at which gestational age?

Accepted Answer

28 weeks

Answer

20 weeks

Answer

24 weeks

Answer

26 weeks

Prenatal Care — MCQs

Prenatal Care — MCQs

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