Maternal-Fetal Medicine Practice Questions

Q: What is the most specific congenital abnormality in a baby born to a diabetic woman?

Sacral agenesis. **Explanation:** In infants of diabetic mothers (IDM), the risk of congenital malformations is 3–4 times higher than in the general population, primarily due to poor glycemic control during organogenesis (the first trimester). **1. Why Sacral Agenesis is Correct:** **Sacral agenesis** (also known as Caudal Regression Syndrome) is considered the **most specific** abnormality associated with maternal diabetes. While it is rare in the general population, a baby born with this condition has a very high probability (nearly 200 times higher risk) of having a mother with diabetes. It involves the incomplete development of the lower spine and can be associated with gastrointestinal and genitourinary anomalies. **2. Analysis of Incorrect Options:** * **A. Ventricular Septal Defect (VSD):** This is the **most common** cardiac malformation in IDMs. However, it is not the most specific, as VSDs occur frequently in the general population due to various other etiologies. * **C. Meningomyelocele:** Neural tube defects are common in IDMs, but they are not as pathognomonic or specific as sacral agenesis. * **D. Transposition of the Great Arteries (TGA):** While TGA is a classic cardiac association with maternal diabetes, VSD remains more frequent, and sacral agenesis remains more specific. **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Malformation Overall:** Cardiovascular system anomalies. * **Most Common Specific Cardiac Defect:** Ventricular Septal Defect (VSD). * **Most Specific Cardiac Defect:** Transposition of the Great Arteries (TGA). * **Most Specific Malformation Overall:** Sacral Agenesis (Caudal Regression Syndrome). * **Transient Hypertrophic Cardiomyopathy:** Often involves asymmetric septal hypertrophy, which usually resolves spontaneously after birth. * **Prevention:** Strict preconception glycemic control (HbA1c < 6.5%) significantly reduces the risk of these anomalies.

Q: What test is used to differentiate maternal from fetal blood?

Apt test. ### Explanation The **Apt test** (also known as the Alkali Denaturation Test) is the gold standard for differentiating fetal hemoglobin (HbF) from adult hemoglobin (HbA). **Mechanism:** The test relies on the biochemical property that **HbF is resistant to alkali**, whereas HbA is not. When a sample (e.g., vaginal blood or gastric aspirate) is mixed with 1% Sodium Hydroxide (NaOH): * **Fetal Blood:** Remains **pink** because HbF resists denaturation. * **Maternal Blood:** Turns **yellow-brown** because HbA denatures into alkaline hematin. **Clinical Application:** It is primarily used in cases of **antepartum hemorrhage** (to rule out **Vasa Previa**, where the bleeding is fetal in origin) or when a neonate presents with bloody vomitus (to determine if the baby swallowed maternal blood during delivery). --- ### Analysis of Other Options: * **A. Osmotic Fragility Test:** Used to diagnose **Hereditary Spherocytosis**. It measures the resistance of RBCs to hemolysis in varying concentrations of hypotonic saline. * **B. Water Bulb Test:** This is not a standard medical test for blood differentiation; it is a distractor. * **D. Kleihauer-Betke (KB) Test:** While also used to identify fetal cells, it is a **quantitative** test used to measure the amount of fetal-maternal hemorrhage (FMH) in the maternal circulation. It is used to calculate the required dose of Anti-D prophylaxis, not for the immediate bedside differentiation of a bloody sample. --- ### High-Yield Clinical Pearls for NEET-PG: * **Apt Test = Qualitative** (Is it fetal or maternal blood?). * **KB Test = Quantitative** (How much fetal blood is in the mother's blood?). * **Vasa Previa Triad:** Rupture of membranes + Painless vaginal bleeding + Fetal bradycardia (Apt test is the diagnostic tool here). * **Limitation:** The Apt test cannot be used if the blood is already clotted or if the sample is contaminated with meconium.

Q: A multigravida with previous 2 normal deliveries presents with unstable lie of the fetus at 34 weeks gestation. What is the most probable cause?

Placenta previa. **Explanation:** An **unstable lie** refers to a situation where the fetal presentation frequently changes (e.g., from transverse to oblique to longitudinal) after 37 weeks, though it is often clinically significant from 34 weeks onwards. **Why Placenta Previa is the Correct Answer:** In a multigravida, the most common cause of an unstable lie is **placenta previa**. When the placenta occupies the lower uterine segment, it acts as a physical barrier, preventing the fetal head from engaging or settling into the maternal pelvis. This "crowding" of the lower segment forces the fetus to remain high and mobile, leading to malpresentations or an unstable lie. **Analysis of Incorrect Options:** * **Oligohydramnios:** Reduced amniotic fluid typically leads to a **fixed** malpresentation (like breech) because the fetus lacks the fluid volume necessary to move or change positions. * **Uterine Anomaly:** While conditions like a subseptate or bicornuate uterus can cause malpresentation, they are more likely to cause a **persistent** malpresentation rather than an unstable lie, and are less common in a multigravida who has already had two normal deliveries. * **Pelvic Contracture:** While a contracted pelvis prevents engagement, it is a less frequent cause of unstable lie in a multigravida compared to placenta previa, as the multiparous uterus is generally more lax. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of unstable lie:** 1. Lax abdominal wall (Multigravida), 2. Placenta previa, 3. Pelvic tumors (Fibroids). * **Management:** At 34 weeks, the management is **expectant** (observation). Active management is only indicated after 37 weeks. * **Risk:** The most dangerous complication of an unstable lie is **Cord Prolapse** following the Spontaneous Rupture of Membranes (SROM).

Q: A 27-year-old has just had an ectopic pregnancy. Which of the following events would be most likely to predispose to ectopic pregnancy?

Pelvic inflammatory disease (PID). **Explanation:** The most common risk factor for ectopic pregnancy is **Pelvic Inflammatory Disease (PID)**. PID, often caused by *Chlamydia trachomatis* or *Neisseria gonorrhoeae*, leads to salpingitis. This inflammation results in the loss of ciliary action in the tubal epithelium and the formation of intratubal adhesions (endosalpingeal scarring). These structural and functional changes delay or prevent the transport of the fertilized ovum to the uterine cavity, leading to implantation within the fallopian tube. **Analysis of Options:** * **Previous tubal surgery (Option A):** While this carries the **highest relative risk** (Odds Ratio) for an ectopic pregnancy, PID is the more common predisposing factor in the general population due to its higher prevalence. * **Use of an IUD (Option C):** IUDs do not *cause* ectopic pregnancy; they are highly effective at preventing all pregnancies. However, if a woman becomes pregnant with an IUD in situ, the *proportion* of those pregnancies being ectopic is higher. * **Induction of ovulation (Option D):** While assisted reproductive technologies (ART) increase the risk of ectopic and heterotopic pregnancies due to hormonal changes and multiple embryos, it is a less frequent cause compared to the widespread incidence of PID. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site of ectopic pregnancy:** Ampulla of the Fallopian tube (70%). * **Most common site of tubal rupture:** Isthmus (due to its narrow lumen). * **Gold Standard Investigation:** Transvaginal Ultrasound (TVS) + Serial β-hCG (Discriminatory zone: 1500–2000 mIU/ml). * **Arias-Stella Reaction:** Hypersecretory endometrium seen on biopsy, characteristic of (but not pathognomonic for) ectopic pregnancy.

Q: What is the best method for assessing fetal well-being at term?

Serial estriol estimation. **Explanation:** The assessment of fetal well-being relies on monitoring the integrity of the **feto-placental unit**. **Why Serial Estriol is the Correct Answer:** Estriol ($E_3$) is the primary estrogen produced during pregnancy. Its synthesis requires a functional pathway involving the mother, the placenta, and the fetus. Specifically, the fetal adrenal glands produce DHEAS, which is hydroxylated in the fetal liver and then converted into estriol by the placenta. Because it requires active participation from fetal organs, a significant drop (usually >40%) in serial maternal urinary or serum estriol levels is a sensitive indicator of fetal compromise or placental insufficiency at term. **Why Other Options are Incorrect:** * **Serial Pregnanediol Estimation:** Pregnanediol is a metabolite of progesterone. Since progesterone is produced solely by the placenta (not requiring fetal precursors), it reflects placental function but does not provide information regarding fetal health. * **Serial HPL (Human Placental Lactogen) Estimation:** HPL is produced by the syncytiotrophoblast of the placenta. Like progesterone, it correlates with placental mass and function rather than direct fetal well-being. **High-Yield Clinical Pearls for NEET-PG:** * **The "Golden Rule":** Estriol reflects the **Feto-Placental Unit**, while HPL and Progesterone reflect only the **Placenta**. * **Modern Practice:** While estriol was historically the "best" biochemical method, in modern clinical practice, it has been largely replaced by the **Biophysical Profile (BPP)** and **Non-Stress Test (NST)** for immediate fetal assessment. * **Low Estriol Levels:** Persistently low estriol is also seen in fetal adrenal hypoplasia, anencephaly, and placental sulfatase deficiency.

Q: At which gestational age is the amount of amniotic fluid typically maximum?

34-36 weeks. The volume of amniotic fluid follows a dynamic pattern throughout pregnancy, reflecting the balance between fetal production (primarily urine) and clearance (primarily swallowing). **Explanation of the Correct Answer:** The amniotic fluid volume increases progressively from the first trimester until it reaches its **peak at 34–36 weeks of gestation**, where the average volume is approximately **800–1000 mL**. After 36 weeks, there is a physiological decline in the volume as the pregnancy approaches term. This peak occurs because, during the late second and early third trimesters, fetal urine production is at its highest relative to the rate of fluid reabsorption through the intramembranous pathway and fetal swallowing. **Analysis of Incorrect Options:** * **A (32–34 weeks):** While the volume is high and increasing during this period, it has not yet reached its maximum physiological plateau. * **C & D (36–40 weeks):** After 36 weeks, the volume begins to decrease. By 40 weeks, the volume typically drops to about 600–800 mL. This reduction continues significantly in post-term pregnancies (beyond 42 weeks), which can lead to oligohydramnios. **High-Yield Clinical Pearls for NEET-PG:** * **Production:** In the first half of pregnancy, fluid is formed by transport across the amnion and fetal skin. After 20 weeks, **fetal urine** is the primary source. * **Clearance:** **Fetal swallowing** is the major route of removal. * **Measurement:** On ultrasound, the **Amniotic Fluid Index (AFI)** is considered normal between 5 and 24 cm. A Single Deepest Pocket (SDP) 8 cm defines polyhydramnios. * **Post-term risk:** At 42 weeks, the volume may decrease to as little as 400 mL, increasing the risk of cord compression.

Question 1

What is the most specific congenital abnormality in a baby born to a diabetic woman?

Accepted Answer

Sacral agenesis

Answer

Ventricular Septal defect

Answer

Meningomyelocele

Answer

Transposition of great arteries

Question 2

For karyotype analysis of stillborns, what is the recommended tissue sample, excluding which option?

Accepted Answer

Fetal skin

Answer

Umbilical cord segment about 1.5 cm long

Answer

Fetal patella

Answer

Placental block taken below cord insertion

Question 3

What test is used to differentiate maternal from fetal blood?

Accepted Answer

Apt test

Answer

Osmotic fragility test

Answer

Water bulb test

Answer

Kleihauer Betke test

Question 4

Aneuploidy is the most common genetic abnormality, accounting for up to 50% of clinical miscarriages. All are true about aneuploidy, EXCEPT?

Accepted Answer

50-60% of fetuses with trisomy 18 die between 12 weeks and 40 weeks gestation.

Answer

30-40% of fetuses with trisomy 21 die between 12 weeks and 40 weeks gestation.

Answer

The occurrence of triploidy is not related to the progression of maternal age.

Answer

In a previous pregnancy with trisomy 21 due to non-disjunction, the risk in a future pregnancy is 0.75% higher.

Question 5

A multigravida with previous 2 normal deliveries presents with unstable lie of the fetus at 34 weeks gestation. What is the most probable cause?

Accepted Answer

Placenta previa

Answer

Oligohydramnios

Answer

Uterine anomaly

Answer

Pelvic contracture

Question 6

A 27-year-old has just had an ectopic pregnancy. Which of the following events would be most likely to predispose to ectopic pregnancy?

Accepted Answer

Pelvic inflammatory disease (PID)

Answer

Previous tubal surgery

Answer

Use of a contraceptive uterine device (IUD)

Answer

Induction of ovulation

Question 7

What is the best method for assessing fetal well-being at term?

Accepted Answer

Serial estriol estimation

Answer

Serial pregnanediol estimation

Answer

Serial HPL estimation

Answer

All of the above

Question 8

At which gestational age is the amount of amniotic fluid typically maximum?

Accepted Answer

34-36 weeks

Answer

32-34 weeks

Answer

36-38 weeks

Answer

38-40 weeks

Question 9

A healthy 23-year-old G1P0 has had an uncomplicated pregnancy to date. She is disappointed because she is 41 weeks gestational age by good dates and a first-trimester ultrasound and wants to have her baby. She feels like she has been pregnant forever and wants to have her baby now. The patient reports good fetal movement; she has been doing kick counts for the past several days and reports that the baby moves about eight times an hour on average. On physical exam, her cervix is firm, posterior, 50% effaced, and 1 cm dilated, and the vertex is at a -1 station. As her obstetrician, what would you recommend to the patient?

Accepted Answer

Continue to monitor kick counts and return to the office in 1 week to reassess the situation

Answer

She should be admitted for an immediate cesarean section

Answer

She should be admitted for Pitocin induction

Answer

Schedule a cesarean section in 1 week if she has not undergone spontaneous labor in the meantime

Question 10

Which of the following statements is true regarding chorionicity in multifetal pregnancy?

Accepted Answer

Chorionicity is accurately determined by first trimester ultrasound scan.

Answer

Monochorionic membranes should have four layers.

Answer

Dichorionic pregnancies are always dizygotic.

Answer

Monochorionic pregnancies are always dizygotic.

Maternal-Fetal Medicine — MCQs

Maternal-Fetal Medicine — MCQs

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