Prenatal Care — MCQs

Prenatal Care Indian Medical PG Practice Questions and MCQs

Question 181: Which of the following is a marker for Down's Syndrome?

A. Increased maternal estriol
B. Decreased maternal serum alpha feto protein (Correct Answer)
C. Decreased HCG
D. Increased CA-125

Explanation: **Explanation:** In Down’s Syndrome (Trisomy 21), specific biochemical markers in the maternal serum undergo characteristic changes during the second trimester (Triple/Quadruple screen). **1. Why Option B is Correct:** Maternal Serum Alpha-Fetoprotein (MSAFP) is produced by the fetal liver and yolk sac. In pregnancies affected by Down’s Syndrome, the MSAFP levels are characteristically **decreased**. While the exact mechanism is not fully understood, it is hypothesized to be due to a decrease in fetal liver production or a smaller-than-average yolk sac in these fetuses. **2. Analysis of Incorrect Options:** * **Option A (Increased Estriol):** In Down’s Syndrome, Unconjugated Estriol (uE3) is actually **decreased**. Estriol production requires a functional fetal adrenal gland and liver; these are often "immature" or less active in Trisomy 21. * **Option C (Decreased HCG):** Human Chorionic Gonadotropin (HCG) is one of the few markers that is **increased** in Down’s Syndrome. This is a high-yield distinction, as most other markers (AFP, uE3) are decreased. * **Option D (Increased CA-125):** CA-125 is a tumor marker primarily used for ovarian cancer monitoring. It is not a standard screening marker for fetal aneuploidy. **3. NEET-PG High-Yield Pearls:** * **The "HI" Rule:** In Down’s Syndrome, only **H**CG and **I**nhibin-A are **High** (Increased). All other markers (AFP, uE3, PAPP-A) are low. * **First Trimester Screen:** Look for **decreased PAPP-A** and **increased Nuchal Translucency (NT)**. * **Edward’s Syndrome (Trisomy 18):** All markers (AFP, HCG, uE3) are **decreased**. * **Neural Tube Defects:** Characterized by **increased AFP** (the opposite of Down’s Syndrome).

Question 182: A 23-year-old female presents with 42 days of amenorrhea and vaginal spotting. Which of the following is the most useful diagnostic test?

A. Transvaginal ultrasonography (Correct Answer)
B. Urine pregnancy test
C. Beta-hCG
D. Serum progesterone

Explanation: **Explanation:** The clinical presentation of **amenorrhea (6 weeks) with vaginal spotting** is a classic triad for early pregnancy complications, most notably **ectopic pregnancy** or threatened abortion. **1. Why Transvaginal Ultrasonography (TVS) is the correct answer:** TVS is the gold standard and the most useful diagnostic tool in this scenario. At 6 weeks (42 days) of gestation, TVS can reliably identify an intrauterine gestational sac (visible at 4.5–5 weeks) or a yolk sac (visible at 5.5 weeks). Its primary utility is to **confirm the location of the pregnancy** (intrauterine vs. ectopic) and assess viability. In a patient with spotting, identifying the pregnancy's location is the immediate clinical priority. **2. Why the other options are incorrect:** * **Urine Pregnancy Test (UPT):** While it confirms pregnancy, it cannot differentiate between a healthy intrauterine pregnancy, a miscarriage, or a life-threatening ectopic pregnancy. * **Beta-hCG:** A single quantitative value is rarely diagnostic. It is most useful when used serially (to check doubling time) or in conjunction with TVS (the "Discriminatory Zone" concept). * **Serum Progesterone:** While low levels (<5 ng/mL) suggest a non-viable pregnancy, it cannot pinpoint the location or provide a definitive diagnosis. **Clinical Pearls for NEET-PG:** * **Discriminatory Zone:** The level of β-hCG at which an intrauterine sac should be visible on TVS is **1500–2000 mIU/mL**. If β-hCG is above this and the uterus is empty, suspect ectopic pregnancy. * **First Sign on TVS:** The "Intrachorionic sac" or "Double decidual sac sign" is the earliest sign of intrauterine pregnancy. * **Management Priority:** In any woman of reproductive age with amenorrhea and abdominal pain/spotting, **Ectopic Pregnancy** must be ruled out first using TVS.

Question 183: What volume of amniotic fluid is typically required for fetal karyotyping?

A. 10 mL
B. 20 mL (Correct Answer)
C. 2-3 mL
D. 3-5 mL

Explanation: **Explanation:** **Amniocentesis** is the gold standard for prenatal genetic diagnosis, typically performed between **15 and 20 weeks** of gestation. 1. **Why 20 mL is correct:** For fetal karyotyping, the goal is to obtain a sufficient concentration of live desquamated fetal cells (amniocytes). Standard clinical practice requires approximately **20 mL** of amniotic fluid. This volume provides an adequate cell count for culture and subsequent metaphase analysis while remaining safe for the pregnancy. At 16 weeks, the total amniotic fluid volume is about 175-225 mL; removing 20 mL represents only about 10% of the total volume, which is quickly regenerated. 2. **Why other options are incorrect:** * **2-3 mL and 3-5 mL:** These volumes are insufficient for routine karyotyping. While they might suffice for PCR-based rapid aneuploidy testing (like QF-PCR or FISH), they do not provide enough cells for a full formal culture. However, 2-3 mL is the standard volume discarded initially during the procedure to avoid maternal cell contamination. * **10 mL:** This is often considered the minimum threshold, but it carries a higher risk of "culture failure." 20 mL is the preferred diagnostic standard to ensure a successful result. **High-Yield NEET-PG Pearls:** * **Timing:** Best performed at **15–20 weeks**. "Early amniocentesis" (before 14 weeks) is avoided due to higher risks of clubfoot (talipes equinovarus) and pregnancy loss. * **Procedure:** Performed under continuous ultrasound guidance using a 20- or 22-gauge needle. * **Complications:** The risk of procedure-related miscarriage is approximately **0.5% (1 in 200)**. * **Rh Status:** Always administer **Anti-D immunoglobulin** to Rh-negative unsensitized mothers following the procedure.

Question 184: Chorionic villous sampling is useful in the diagnosis of all the following conditions except?

A. Tay-Sachs disease
B. Spina bifida (Correct Answer)
C. Thalassemia
D. Down syndrome

Explanation: **Explanation:** The correct answer is **Spina bifida**. **1. Why Spina bifida is the correct answer:** Chorionic Villous Sampling (CVS) involves obtaining a sample of placental tissue (chorionic villi) to analyze the fetal genome. It is used to detect **genetic, chromosomal, and metabolic disorders**. Spina bifida is a **Neural Tube Defect (NTD)**, which is a structural malformation, not a primary genetic sequence error. The diagnosis of NTDs relies on identifying elevated levels of **Alpha-fetoprotein (AFP)** in maternal serum or amniotic fluid, and visualization via **Targeted Ultrasonography**. Since CVS does not measure AFP levels, it cannot be used to diagnose Spina bifida. **2. Analysis of incorrect options:** * **Tay-Sachs disease:** This is an autosomal recessive lysosomal storage disorder. It can be diagnosed via CVS through DNA analysis or enzyme assay of the villi. * **Thalassemia:** As a single-gene disorder (hemoglobinopathy), it is diagnosed using DNA amplification (PCR) from the fetal cells obtained during CVS. * **Down syndrome:** This is a chromosomal aneuploidy (Trisomy 21). CVS allows for a full fetal karyotype or FISH analysis, making it a definitive diagnostic tool for chromosomal abnormalities. **3. NEET-PG High-Yield Pearls:** * **Timing:** CVS is typically performed between **10–13 weeks** of gestation (earlier than amniocentesis). * **Risk:** Performing CVS before 9 weeks is associated with **Limb Reduction Defects**. * **Advantage:** It provides earlier results compared to amniocentesis, allowing for safer first-trimester termination if necessary. * **Limitation:** It cannot detect NTDs and carries a small risk of **Confined Placental Mosaicism**, which may require follow-up amniocentesis.

Question 185: Fetal alcohol syndrome is characterized by which of the following features?

A. Large palpebral fissures
B. Thin vermillion border (Correct Answer)
C. Macrosomia
D. Hyperplastic philtrum

Explanation: **Explanation:** Fetal Alcohol Syndrome (FAS) is a leading preventable cause of intellectual disability, resulting from maternal alcohol consumption during pregnancy. The ethanol acts as a potent teratogen, disrupting cell division and migration during critical periods of organogenesis. **1. Why the Correct Answer is Right:** The diagnosis of FAS relies on a classic triad of clinical features: growth restriction, central nervous system (CNS) involvement, and characteristic facial dysmorphism. The **thin vermillion border** (a very thin upper lip) is one of the three cardinal facial features, alongside a **smooth philtrum** (loss of the vertical groove between the nose and upper lip) and **short palpebral fissures**. **2. Why the Incorrect Options are Wrong:** * **A. Large palpebral fissures:** In FAS, the palpebral fissures (the opening between the eyelids) are characteristically **short** or small, not large. * **C. Macrosomia:** FAS is associated with **prenatal and postnatal growth restriction** (small for gestational age). Macrosomia is typically associated with gestational diabetes. * **D. Hyperplastic philtrum:** The philtrum in FAS is **hypoplastic or smooth** (flattened). A hyperplastic or prominent philtrum is not a feature of this syndrome. **Clinical Pearls for NEET-PG:** * **Most sensitive period:** The first trimester is the most critical period for structural malformations (facial dysmorphism). * **CNS findings:** Microcephaly, intellectual disability, and ADHD are common. * **Cardiac defects:** Ventricular Septal Defect (VSD) is the most common cardiac association. * **Skeletal:** Hockey-stick palmar crease is a high-yield physical sign sometimes noted. * **Safe Limit:** There is **no known safe amount** of alcohol consumption during pregnancy.

Question 186: What is the optimal gestational age for performing chorionic villus sampling for prenatal diagnosis?

A. 8-10 weeks
B. 10-12 weeks (Correct Answer)
C. 12-14 weeks
D. 14-16 weeks

Explanation: **Explanation:** **Chorionic Villus Sampling (CVS)** is a prenatal diagnostic procedure used to obtain fetal tissue for genetic analysis. The optimal timing for CVS is **10–13 weeks** (most commonly cited as **10–12 weeks** in standard textbooks like Williams Obstetrics). 1. **Why 10–12 weeks is correct:** At this stage, the chorion frondosum is well-developed, providing sufficient tissue for sampling while remaining early enough to allow for a safer first-trimester termination if an abnormality is detected. 2. **Why other options are incorrect:** * **8–10 weeks (Option A):** Performing CVS before 10 weeks is contraindicated due to a significantly increased risk of **limb reduction defects** (oromandibular-limb hypogenesis) and fetal loss. * **12–14 weeks (Option C):** While technically possible, as the pregnancy progresses toward the second trimester, the chorion begins to thin, and **Amniocentesis** (typically performed after 15 weeks) becomes the preferred diagnostic modality. * **14–16 weeks (Option D):** This is the standard window for early amniocentesis, not CVS. **High-Yield Clinical Pearls for NEET-PG:** * **Route:** CVS can be performed **transabdominally** or **transcervically**, depending on placental location. * **Complication:** The most specific risk associated with early CVS (<10 weeks) is **Limb Reduction Defects**. * **Limitation:** CVS cannot detect **Neural Tube Defects (NTDs)** because it does not measure Alpha-fetoprotein (AFP) in the amniotic fluid. * **Confirmatory Test:** If **Confined Placental Mosaicism** is suspected (where the placenta has a different genetic makeup than the fetus), an amniocentesis must be performed for confirmation.

Question 187: After how many days of ovulation does embryo implantation occur?

A. 3-5 days
B. 7-9 days (Correct Answer)
C. 10-12 days
D. 13-15 days

Explanation: **Explanation:** The correct answer is **B. 7-9 days**. **Medical Concept:** Following ovulation, fertilization typically occurs in the ampulla of the fallopian tube within 12–24 hours. The zygote then undergoes cleavage as it travels toward the uterus. It reaches the uterine cavity as a **morula** on day 3–4 and transforms into a **blastocyst** by day 5. Implantation begins when the blastocyst apposes and adheres to the endometrium (decidua), which occurs during the "implantation window." This process typically starts **6–7 days after fertilization** (which closely follows ovulation) and is completed by day 9–10. Therefore, the 7–9 day range is the most accurate clinical window for active implantation. **Analysis of Incorrect Options:** * **A. 3-5 days:** At this stage, the conceptus is still a morula or an early blastocyst either traveling through the fallopian tube or just entering the uterine cavity; it has not yet begun the process of implantation. * **C. 10-12 days:** By this time, implantation is usually complete, and the blastocyst is fully embedded within the endometrium. * **D. 13-15 days:** This corresponds to the time of the missed period and the beginning of the production of detectable levels of hCG in maternal urine. **NEET-PG High-Yield Pearls:** * **Implantation Window:** Occurs during the mid-luteal phase (Days 20–24 of a 28-day cycle). * **Site of Implantation:** Most commonly the upper posterior wall of the uterine body. * **hCG Detection:** Human Chorionic Gonadotropin (hCG) can be detected in maternal serum as early as **8–9 days after ovulation** (immediately following implantation). * **Trophoblast:** It is the outer layer of the blastocyst that differentiates into the cytotrophoblast and syncytiotrophoblast to facilitate invasion.

Question 188: Which of the following is a method of Non-Invasive Prenatal Testing (NIPT)?

A. Testing performed on maternal tissue
B. Amniocentesis for evaluation of fetal chromosomal anomalies
C. Preconception gene testing on ova
D. Maternal serum testing for Down's Syndrome (Correct Answer)

Explanation: **Explanation:** **Non-Invasive Prenatal Testing (NIPT)** refers to screening methods that assess the risk of fetal genetic abnormalities without entering the uterine cavity, thereby posing no risk of miscarriage. The most common application is the analysis of **cell-free fetal DNA (cffDNA)** or biochemical markers circulating in the **maternal serum**. **Why Option D is Correct:** Maternal serum testing (such as the Combined Test, Quadruple Screen, or cffDNA analysis) is the hallmark of non-invasive screening. These tests analyze substances like PAPP-A, hCG, or fetal DNA fragments found in the mother's blood to screen for aneuploidies like Down’s Syndrome (Trisomy 21). **Why Other Options are Incorrect:** * **Option A:** NIPT specifically targets fetal genetic material or markers found in maternal circulation, not the mother’s own physical tissues. * **Option B:** Amniocentesis is an **invasive** procedure involving a needle puncture of the amniotic sac. While it is the "gold standard" for diagnosis, it carries a small risk of pregnancy loss. * **Option C:** Preconception testing on ova is a form of carrier screening or part of Preimplantation Genetic Testing (PGT); it is not considered "prenatal" testing as it occurs before a pregnancy is established. **High-Yield Clinical Pearls for NEET-PG:** * **Timing:** cffDNA testing can be performed as early as **10 weeks** of gestation. * **Source:** cffDNA originates from the **trophoblast** (placenta), not the fetus directly. * **Confirmatory Rule:** NIPT is a **screening test**, not a diagnostic one. Any positive result must be confirmed via invasive testing (CVS or Amniocentesis). * **Fetal Fraction:** For a valid cffDNA result, the fetal fraction must typically be **>4%**.

Question 189: Which of the following statements is false regarding the use of MRI in obstetric practice?

A. MRI should be avoided in the first trimester of pregnancy.
B. Fetal anatomy is well displayed even in the presence of oligohydramnios.
C. Spinal and intracranial anomalies are clearly defined.
D. Placental abnormalities are not picked up. (Correct Answer)

Explanation: ### Explanation **1. Why Option D is the correct (False) statement:** MRI is an excellent modality for evaluating **placental abnormalities**, particularly **Placenta Accreta Spectrum (PAS)** and placental tumors. While ultrasound with Doppler is the first-line screening tool, MRI provides superior soft-tissue contrast and a wider field of view, making it the gold standard for assessing the depth of placental invasion into the myometrium or adjacent organs (like the bladder) and for diagnosing posterior placentation where ultrasound may be limited. **2. Analysis of Incorrect Options:** * **Option A (True):** Although there is no documented evidence of fetal harm from MRI, guidelines (like those from the ACR and ACOG) generally recommend **avoiding MRI in the first trimester** unless the information is urgently needed and cannot be obtained via ultrasound. This is a precautionary measure during the period of organogenesis. * **Option B (True):** Unlike ultrasound, which requires an adequate "acoustic window" of amniotic fluid, **MRI signal is not affected by oligohydramnios**. It provides high-resolution images of the fetus even when fluid levels are low. * **Option C (True):** MRI is highly sensitive for **CNS anomalies**. It is the preferred follow-up modality for suspected ventriculomegaly, agenesis of the corpus callosum, and posterior fossa malformations, as it provides superior detail of the developing brain parenchyma and spinal cord. ### High-Yield Clinical Pearls for NEET-PG: * **Gadolinium Contrast:** It is generally **contraindicated** in pregnancy (Category C) as it crosses the placenta, enters the amniotic fluid, and may cause fetal risks. * **Safety:** MRI does not use ionizing radiation, making it safer than CT scans for fetal imaging. * **Best Time for Fetal MRI:** Usually performed after **18–22 weeks** of gestation when fetal organs are larger and movement is slightly more restricted. * **Specific Use:** MRI is the investigation of choice for suspected **fetal diaphragmatic hernia** (to calculate lung volume) and **fetal tumors** (like sacrococcygeal teratoma).

Question 190: Which of the following is true regarding asymptomatic bacteriuria in pregnancy?

A. Most cases are asymptomatic in pregnancy. (Correct Answer)
B. If untreated, it often progresses to pyelonephritis.
C. Early and prompt treatment prevents fetal abnormalities.
D. It increases the chance of premature infant delivery.

Explanation: **Explanation:** **Asymptomatic Bacteriuria (ASB)** is defined as the presence of $>10^5$ colony-forming units (CFU)/mL of a single uropathogen in a midstream clean-catch urine specimen from an individual without symptoms of a urinary tract infection. 1. **Why Option A is correct:** By definition, ASB is asymptomatic. In pregnancy, the prevalence is approximately 2–10%. Because patients do not present with symptoms (dysuria, frequency), it can only be detected through routine screening (ideally at the first prenatal visit or between 12–16 weeks). 2. **Why Option B is incorrect:** While it is true that untreated ASB can progress to pyelonephritis in 20–40% of cases, the statement "often progresses" is statistically less accurate than the defining characteristic that most cases are asymptomatic. 3. **Why Option C is incorrect:** Treatment of ASB is primarily aimed at preventing maternal pyelonephritis and reducing the risk of preterm labor/low birth weight. It does **not** prevent congenital fetal abnormalities, as the bacteria do not typically have teratogenic effects. 4. **Why Option D is incorrect:** While ASB is associated with an increased risk of preterm delivery and low birth weight, Option A remains the most fundamental "true" statement regarding the nature of the condition itself. **High-Yield NEET-PG Pearls:** * **Most common organism:** *Escherichia coli* (70–80%). * **Screening:** Recommended for all pregnant women at the first visit via **Urine Culture** (Gold Standard). * **Treatment:** Essential even if asymptomatic. Common drugs include Nitrofurantoin (avoid near term), Amoxicillin, or Cephalexin. * **Complication:** Untreated ASB is the most common precursor to **acute pyelonephritis** in the second and third trimesters.

Practice by Chapter

Preconception Counseling

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Pregnancy Diagnosis and Dating

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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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