Maternal-Fetal Medicine Practice Questions

Q: Which measurement correlates with the suboccipitobregmatic diameter of the fetal skull?

10 cm. The **Suboccipitobregmatic (SOB) diameter** is the most important diameter of the fetal skull in clinical obstetrics, as it is the presenting diameter in a well-flexed vertex presentation. ### 1. Why the Correct Answer is Right The **Suboccipitobregmatic diameter** extends from the undersurface of the occiput (at the junction of the neck) to the center of the anterior fontanelle (bregma). Its measurement is **9.5 cm**. In the context of NEET-PG and standard textbooks like Williams Obstetrics or Dutta’s Textbook of Obstetrics, while the precise measurement is 9.5 cm, **10 cm** is the closest clinical approximation provided in the options. It represents the smallest possible diameter, allowing for the easiest passage through the birth canal. ### 2. Analysis of Incorrect Options * **A. 9.4 cm:** While very close to 9.5 cm, standard medical entrance exams traditionally pair the SOB diameter with the 9.5–10 cm range. * **C. 11.3 cm:** This correlates with the **Suboccipitofrontal (SOF)** diameter (10 cm) or the **Occipitofrontal (OF)** diameter (11.5 cm), which is the presenting diameter in a deflexed vertex (military) position. * **D. 12 cm:** This correlates with the **Submentobregmatic (SMB)** diameter (9.5 cm) or the **Mentovertical (MV)** diameter, which is the largest diameter (13.5 cm) seen in brow presentations. ### 3. High-Yield Clinical Pearls for NEET-PG * **Smallest Diameter:** Suboccipitobregmatic (9.5 cm) – seen in complete flexion. * **Largest Diameter:** Mentovertical (13.5 cm) – seen in brow presentation; usually necessitates a C-section. * **Mento-Vertical (MV):** 13.5 cm (Brow presentation). * **Submentobregmatic (SMB):** 9.5 cm (Face presentation). * **Occipitofrontal (OF):** 11.5 cm (Deflexed head/Military position). * **Biparietal Diameter (BPD):** 9.5 cm (Transverse diameter).

Q: The antiretroviral regime administration in the peripartum period decreases the risk of vertical transmission by:

50%. The risk of vertical transmission of HIV from mother to child occurs at three stages: intrauterine (in utero), intrapartum (during labor and delivery), and postpartum (through breastfeeding). **Explanation of the Correct Answer:** Without any intervention, the overall risk of mother-to-child transmission (MTCT) is approximately 25–30%. The **intrapartum period** is the most critical window, accounting for nearly **50-60%** of all transmissions due to fetal exposure to infected maternal blood and cervicovaginal secretions during labor. Administering an effective antiretroviral (ARV) regimen specifically during the peripartum period (labor and delivery) targets this high-risk window, effectively reducing the transmission risk by approximately **50%**. **Analysis of Incorrect Options:** * **A (30%):** This understates the impact of peripartum prophylaxis. While any ARV use helps, the specific reduction attributed to intrapartum intervention is more robust. * **C & D (65% & 75%):** These figures are more representative of the *cumulative* reduction seen when combining antenatal ARVs with intrapartum and neonatal prophylaxis. A full HAART (Highly Active Antiretroviral Therapy) regimen started early in pregnancy can reduce the risk to less than 1-2%. **NEET-PG High-Yield Pearls:** * **Most common route of MTCT:** Intrapartum (during labor). * **Drug of Choice (WHO/NACO):** TLE Regimen (Tenofovir + Lamivudine + Efavirenz) lifelong for the mother, regardless of CD4 count. * **Infant Prophylaxis:** Syrup Nevirapine for 6 weeks (extend to 12 weeks if maternal ART duration was 1000 copies/mL or unknown. If the viral load is <50 copies/mL, vaginal delivery is preferred.

Q: All of the following are used in inherited thrombophilia testing in pregnancy, except:

Lupus anticoagulant. **Explanation:** The core of this question lies in distinguishing between **inherited** and **acquired** thrombophilias. **Why Lupus Anticoagulant is the correct answer:** Lupus anticoagulant (LA) is a component of **Antiphospholipid Antibody Syndrome (APS)**, which is an **acquired** autoimmune thrombophilia. While it is a significant cause of recurrent pregnancy loss and maternal thrombosis, it is not a genetic/inherited condition. Therefore, it does not belong in a panel for *inherited* thrombophilia testing. **Analysis of incorrect options (Inherited Thrombophilias):** * **Antithrombin (AT) deficiency (Option A):** An inherited deficiency. It is the most thrombogenic of all inherited thrombophilias, carrying the highest risk of venous thromboembolism (VTE) during pregnancy. * **Protein C deficiency (Option B):** An inherited autosomal dominant condition. Along with Protein S deficiency, it leads to a failure in neutralizing Factors Va and VIIIa. * **Factor V Leiden mutation (Option C):** The **most common** inherited thrombophilia in Caucasian populations. It involves a point mutation that makes Factor V resistant to inactivation by activated Protein C. **Clinical Pearls for NEET-PG:** * **Most common inherited thrombophilia:** Factor V Leiden mutation. * **Highest risk of VTE in pregnancy:** Antithrombin III deficiency. * **Testing Caution:** Protein S levels naturally decrease during pregnancy; therefore, testing for Protein S deficiency is unreliable during the gestational period and should be done postpartum. * **Screening Indication:** Inherited thrombophilia screening is generally indicated for women with a personal history of VTE or a first-degree relative with high-risk thrombophilia.

Q: MgSO4 is contraindicated in eclampsia during treatment EXCEPT when which of the following occurs?

Respiratory rate is < 16/min. **Explanation:** Magnesium sulfate ($MgSO_4$) is the drug of choice for controlling and preventing seizures in eclampsia. However, it has a narrow therapeutic index and is excreted solely by the kidneys. Monitoring for magnesium toxicity is critical to prevent respiratory paralysis and cardiac arrest. **Why Option B is the Correct Answer:** The question asks when $MgSO_4$ is **NOT** contraindicated (i.e., when it can still be administered). According to standard protocols (Pritchard’s regimen), the clinical monitoring parameters for continuing $MgSO_4$ are: 1. **Respiratory Rate (RR) $\geq$ 12–14/min:** A rate of **16/min** is within the normal range and indicates no respiratory depression. Therefore, $MgSO_4$ is **not** contraindicated at this rate. 2. **Presence of Patellar Reflex (Knee Jerk):** Its disappearance is the first sign of toxicity. 3. **Urine Output $\geq$ 30 ml/hr:** To ensure adequate drug clearance. **Analysis of Incorrect Options:** * **Option A (Urine output < 30 ml/hr):** This indicates renal impairment. Since $MgSO_4$ is excreted by kidneys, continuing it would lead to toxic accumulation. * **Option D (Knee jerk is absent):** Loss of deep tendon reflexes (DTRs) occurs at plasma levels of 7–10 mEq/L and is the earliest warning sign of toxicity. Administration must be stopped. * **Option C (Diastolic BP < 90 mmHg):** While not a direct contraindication for $MgSO_4$ toxicity, it is irrelevant to the specific safety monitoring of Magnesium. $MgSO_4$ is an anticonvulsant, not primarily an antihypertensive. **High-Yield Clinical Pearls for NEET-PG:** * **Therapeutic range:** 4–7 mEq/L. * **Sequence of Toxicity:** Loss of Knee Jerk (7–10 mEq/L) $\rightarrow$ Respiratory Depression (11–15 mEq/L) $\rightarrow$ Cardiac Arrest (>15 mEq/L). * **Antidote:** 10 ml of 10% **Calcium Gluconate** IV (administered slowly over 10 minutes).

Q: A Rh negative G4P3+0 patient has an antibody level of 15 IU/ml (IAT 1:32) at 27 weeks gestation. What is the most appropriate next step in management?

Estimate middle cerebral artery peak systolic velocity. In Rh-isoimmunized pregnancies, the management goal is to detect fetal anemia before hydrops develops. **Explanation of the Correct Answer:** The patient is sensitized (Antibody titer ≥ 1:16 or > 4 IU/ml), which puts the fetus at risk for Hemolytic Disease of the Fetus and Newborn (HDFN). **Middle Cerebral Artery Peak Systolic Velocity (MCA-PSV)** is the current gold standard for non-invasive screening of fetal anemia. * **Mechanism:** In fetal anemia, blood viscosity decreases and cardiac output increases to maintain oxygen delivery. This results in a higher velocity of blood flow. * **Threshold:** An MCA-PSV **> 1.5 MoM** (Multiples of Median) indicates severe anemia and is the trigger for invasive intervention. **Why Other Options are Incorrect:** * **A. Amniotic fluid bilirubin (Liley’s Chart):** Historically used to measure ΔOD450, this is now largely obsolete because it is invasive and less accurate than MCA-PSV, especially in the second trimester. * **B. Cordocentesis:** This is an invasive procedure with a 1-2% risk of fetal loss. It is used for definitive diagnosis and to prepare for transfusion, but it is not the *initial* screening step. * **D. Intrauterine Transfusion (IUT):** This is a therapeutic intervention, not a diagnostic step. It is only performed if fetal hemoglobin is confirmed to be 2 SD below the mean for gestational age. **Clinical Pearls for NEET-PG:** * **Critical Titer:** 1:16 is generally considered the threshold for monitoring; below this, the risk of hydrops is negligible. * **Best Timing:** MCA-PSV is most accurate between 18 and 35 weeks of gestation. * **First Step in Sensitized Pregnancy:** Always determine the paternal Rh status and zygosity first. If the father is heterozygous, fetal RHD genotyping (via cffDNA) is the next step.

Q: Monochorionic monoamniotic twin occurs if division occurs:

> 8 days. The timing of the division of a single fertilized ovum determines the chorionicity and amniocity of monozygotic twins. The later the division occurs, the more structures the twins must share. **Explanation of the Correct Answer:** * **Option D (> 8 days):** If the zygote divides between **8 and 13 days** post-fertilization, the implantation has already occurred, and the amniotic sac has begun to form. Consequently, the twins will share a single placenta (Monochorionic) and a single amniotic sac (Monoamniotic). If division occurs even later (>13 days), it results in conjoined twins. **Analysis of Incorrect Options:** * **Option A & B (0–4 days):** Division at the **morula stage** (within the first 3–4 days) occurs before the differentiation of the trophoblast. This results in **Dichorionic Diamniotic (DCDA)** twins, where each fetus has its own placenta and sac. * **Option C (4–8 days):** Division at the **blastocyst stage** occurs after the trophoblast has differentiated but before the amnion forms. This results in **Monochorionic Diamniotic (MCDA)** twins, which is the most common type of monozygotic twinning (approx. 75%). **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic (Di-Di, Mo-Di, Mo-Mo):** * 0–4 days: **Di**-Di (2 chorions, 2 amnions) * 4–8 days: **Mo**-Di (1 chorion, 2 amnions) * 8–12 days: **Mo**-Mo (1 chorion, 1 amnion) * >13 days: Conjoined twins. * **T-sign vs. Lambda sign:** On ultrasound, the "T-sign" indicates Monochorionic twins, while the "Lambda (λ) or Twin-peak sign" indicates Dichorionic twins. * **Risk:** Mo-Mo twins carry the highest risk of cord entanglement and fetal demise, often requiring elective delivery between 32–34 weeks.

Q: What is the best method for diagnosing the degree of placenta previa?

Transvaginal sonography. **Explanation:** **1. Why Transvaginal Sonography (TVS) is the Correct Answer:** Transvaginal sonography is currently the **gold standard** for diagnosing the degree and location of placenta previa. Unlike transabdominal scans (TAS), which can be obscured by maternal obesity, a full bladder (causing a false-positive diagnosis due to cervical compression), or the fetal head, TVS provides high-resolution images of the internal os and the placental edge. It is **safe, accurate, and superior** to TAS, with a sensitivity and specificity of nearly 100%. Contrary to old myths, TVS does not increase the risk of bleeding because the probe is not inserted into the cervical canal. **2. Why Other Options are Incorrect:** * **Double set-up examination:** Historically used to diagnose previa by palpating the cervix in an OR prepared for immediate CS. It is now **obsolete** and contraindicated due to the high risk of provoking massive hemorrhage. * **Observation during Cesarean section:** While this confirms the diagnosis, it is not a "diagnostic method" used for planning management; diagnosis must be established pre-operatively to determine the mode of delivery. * **Examination of the placenta after delivery:** This can show the distance from the tear to the placental edge, but it is a retrospective finding and has no clinical utility in active management. **Clinical Pearls for NEET-PG:** * **The "Gold Standard":** TVS is the investigation of choice. * **Safe Distance:** If the placental edge is **>2 cm** from the internal os, a vaginal delivery is usually successful. If it is **<2 cm or overlapping**, a Cesarean section is indicated. * **Warning:** Never perform a digital vaginal examination (PV) in a case of suspected placenta previa until the diagnosis is ruled out by ultrasound (the "Stallworthy’s sign" concept).

Question 1

Which measurement correlates with the suboccipitobregmatic diameter of the fetal skull?

Accepted Answer

10 cm

Answer

9.4 cm

Answer

11.3 cm

Answer

12 cm

Question 2

The antiretroviral regime administration in the peripartum period decreases the risk of vertical transmission by:

Accepted Answer

50%

Answer

30%

Answer

65%

Answer

75%

Question 3

All of the following are used in inherited thrombophilia testing in pregnancy, except:

Accepted Answer

Lupus anticoagulant

Answer

Antithrombin deficiency

Answer

Protein C deficiency

Answer

Factor V Leiden mutation

Question 4

MgSO4 is contraindicated in eclampsia during treatment EXCEPT when which of the following occurs?

Accepted Answer

Respiratory rate is < 16/min

Answer

Urine output is < 30 ml/hr

Answer

Diastolic blood pressure is < 90 mmHg

Answer

Knee jerk is absent

Question 5

A Rh negative G4P3+0 patient has an antibody level of 15 IU/ml (IAT 1:32) at 27 weeks gestation. What is the most appropriate next step in management?

Accepted Answer

Estimate middle cerebral artery peak systolic velocity

Answer

Estimate amniotic fluid bilirubin levels

Answer

Estimate fetal hemoglobin levels by cordocentesis

Answer

Perform intrauterine transfusion

Question 6

Monochorionic monoamniotic twin occurs if division occurs:

Accepted Answer

> 8 days

Answer

Before 24 hours

Answer

1-4 days

Answer

4-8 days

Question 7

A 24-year-old woman at 8 weeks of gestation presents with a history of pulmonary embolism 7 years ago during her first pregnancy. She was treated with intravenous heparin followed by several months of oral warfarin and has had no further evidence of thromboembolic disease for over 6 years. Which of the following statements about her current condition is true?

Accepted Answer

The patient should be placed on low-dose heparin therapy throughout pregnancy and puerperium.

Answer

Having no evidence of disease for over 5 years means that the risk of thromboembolism is not greater than normal.

Answer

Impedance plethysmography is not a useful study to evaluate for deep venous thrombosis in pregnancy.

Answer

Doppler ultrasonography is not a useful technique to evaluate for deep venous thrombosis in pregnancy.

Question 8

Which of the following situations poses the greatest risk of Rh incompatibility?

Accepted Answer

Rh-ve mother with a second Rh+ve child

Answer

Rh+ve mother with a second Rh-ve child

Answer

Rh+ve mother with a first Rh-ve child

Answer

Rh-ve mother with a first Rh+ve child

Question 9

Maternal near miss refers to:

Accepted Answer

A woman presenting with a life-threatening condition but has survived

Answer

Teenager becoming pregnant

Answer

Contraceptive failure in a teenager

Answer

A woman presenting with a life-threatening condition who has died

Question 10

What is the best method for diagnosing the degree of placenta previa?

Accepted Answer

Transvaginal sonography

Answer

Double set-up examination

Answer

Observation during Cesarean section

Answer

Examination of the placenta after delivery

Maternal-Fetal Medicine — MCQs

Maternal-Fetal Medicine — MCQs

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