Prenatal Care Practice Questions

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.

Q: Which of the following is NOT a diagnostic serum marker for Down's syndrome?

Progesterone. **Explanation:** In prenatal screening for Down’s syndrome (Trisomy 21), specific biochemical markers are measured to assess risk. **Progesterone (Option D)** is the correct answer because it is not used as a diagnostic or screening marker for chromosomal aneuploidies. While progesterone is vital for maintaining pregnancy, its levels do not show a consistent, predictive correlation with Down’s syndrome. **Analysis of Screening Markers:** The "Triple Test" (performed between 15–20 weeks) utilizes the other three options. In a pregnancy affected by Down’s syndrome, the typical pattern is: * **Alpha-fetoprotein (AFP) (Option B):** Levels are **decreased**. AFP is produced by the fetal yolk sac and liver. * **Free Estriol (uE3) (Option A):** Levels are **decreased**. It reflects the integrity of the fetal-placental unit. * **hCG (Option C):** Levels are **increased**. This is a characteristic finding in Trisomy 21. **High-Yield Clinical Pearls for NEET-PG:** 1. **Quadruple Test:** Adds **Inhibin-A** to the triple test. In Down’s syndrome, Inhibin-A levels are **increased** (Mnemonic: **HI**gh = **H**CG and **I**nhibin are elevated). 2. **First Trimester Screening (11–13.6 weeks):** Uses **PAPP-A** (decreased) and **free β-hCG** (increased), combined with Nuchal Translucency (NT) ultrasound. 3. **Edward Syndrome (Trisomy 18):** Unlike Down’s syndrome, **all** markers (AFP, uE3, and hCG) are typically **decreased**. 4. **Neural Tube Defects (NTD):** Characterized by significantly **elevated AFP** levels.

Q: Alpha-fetoprotein levels are increased in all conditions EXCEPT:

Down's syndrome. **Explanation:** Alpha-fetoprotein (AFP) is a glycoprotein synthesized initially by the yolk sac and later by the fetal liver. It is the fetal equivalent of albumin. Understanding its levels is crucial for prenatal screening. **Why Down’s Syndrome is the Correct Answer:** In **Down’s Syndrome (Trisomy 21)**, maternal serum AFP (MSAFP) levels are characteristically **decreased** (usually <0.5 MoM). The exact mechanism is not fully understood, but it is attributed to reduced synthesis by the fetal liver and a smaller-than-normal yolk sac. This is a classic "Triple Test" finding, where AFP and Unconjugated Estriol (uE3) are low, while hCG and Inhibin-A are elevated. **Analysis of Incorrect Options:** * **Open Neural Tube Defects (NTDs):** Conditions like anencephaly or spina bifida aperta allow AFP to leak directly from the fetal circulation/CSF into the amniotic fluid and then into the maternal serum, causing **elevated** levels. * **Twin Pregnancy:** AFP levels are proportional to the number of fetuses. In multifetal gestations, the combined production leads to **increased** MSAFP. * **Intrauterine Fetal Demise (IUFD):** Fetal death leads to the breakdown of fetal tissues and increased permeability of the skin/placental barrier, causing a massive release of AFP into the maternal circulation. **NEET-PG High-Yield Pearls:** * **Most common cause of increased MSAFP:** Incorrect dating (underestimation of gestational age). * **Other causes of increased AFP:** Omphalocele, Gastroschisis, Turner syndrome (with cystic hygroma), and Renal anomalies (Finnish-type nephrosis). * **Other causes of decreased AFP:** Edwards syndrome (Trisomy 18), Molar pregnancy, and Maternal obesity. * **Optimal timing for MSAFP screening:** 15 to 20 weeks (ideal: 16–18 weeks).

Question 1

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 2

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 3

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 4

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 5

What is the commonest chromosomal anomaly leading to spontaneous abortions?

Accepted Answer

Trisomy 16

Answer

Trisomy 21

Answer

Tetraploidy

Answer

Turner's syndrome

Question 6

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 7

Maximum cardiac output in pregnancy occurs at which gestational age?

Accepted Answer

28 weeks

Answer

20 weeks

Answer

24 weeks

Answer

26 weeks

Question 8

Which of the following is NOT a diagnostic serum marker for Down's syndrome?

Accepted Answer

Progesterone

Answer

Free estriol

Answer

Alpha-fetoprotein

Answer

hCG

Question 9

Alpha-fetoprotein levels are increased in all conditions EXCEPT:

Accepted Answer

Down's syndrome

Answer

Open neural tube defects

Answer

Twin pregnancy

Answer

Intrauterine fetal demise

Question 10

All of the following are true about Nuchal Translucency scan except?

Accepted Answer

Increased nuchal translucency is associated with aneuploidy.

Answer

It is done between 11 weeks and 0 days to 13 weeks and 6 days of gestation.

Answer

It is performed in a neutral head position in the mid-sagittal plane.

Answer

The nuchal translucency measurement is reliable when the Crown-Rump Length (CRL) is between 45 mm and 84 mm.

Prenatal Care — MCQs

Prenatal Care — MCQs

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