Maternal-Fetal Medicine — MCQs

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?

Q220Medium

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

Maternal-Fetal Medicine Indian Medical PG Practice Questions and MCQs

Question 211: What is the most specific congenital abnormality in a baby born to a diabetic woman?

A. Ventricular Septal defect
B. Sacral agenesis (Correct Answer)
C. Meningomyelocele
D. Transposition of great arteries

Explanation: **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.

Question 212: For karyotype analysis of stillborns, what is the recommended tissue sample, excluding which option?

A. Umbilical cord segment about 1.5 cm long
B. Fetal patella
C. Placental block taken below cord insertion
D. Fetal skin (Correct Answer)

Explanation: **Explanation:** The primary goal in obtaining tissue for karyotype analysis in a stillborn is to secure **viable cells** (fibroblasts) that can be successfully cultured. In a stillbirth, the fetus has often undergone varying degrees of autolysis (maceration), which leads to cell death in superficial tissues. **Why Fetal Skin is the Correct Answer (The Exception):** Historically, fetal skin was the standard sample. However, current guidelines (ACOG and SMFM) now **discourage** fetal skin biopsies because skin cells are highly susceptible to autolysis and have the highest rate of culture failure in stillborns. Therefore, it is the option to be excluded in favor of deeper, more protected tissues. **Analysis of Other Options:** * **Umbilical Cord (A):** A 1–2 cm segment of the umbilical cord is an excellent source. It is rich in myofibroblasts and is often better preserved than fetal skin, offering a high success rate for cell culture. * **Fetal Patella (B):** Cartilage and connective tissue from the patella (or other long bones) are highly resistant to autolysis. These "deep" samples are the gold standard for macerated fetuses because the cells remain viable long after the skin has degraded. * **Placental Block (C):** A 1 cm cube of placental tissue taken from the fetal side (subchorionic), specifically near the cord insertion, provides viable chorionic villi which are excellent for cytogenetic analysis. **High-Yield Clinical Pearls for NEET-PG:** * **Success Rates:** Culture success is highest with the **umbilical cord and patella/cartilage**, and lowest with fetal skin. * **Preferred Method:** If available, **Chromosomal Microarray (CMA)** is now preferred over traditional karyotyping for stillbirths as it can be performed on dead (non-viable) tissue and has a higher diagnostic yield. * **Procedure:** Samples should be placed in **Hank’s Balanced Salt Solution** or viral transport media, never in formalin, as formalin fixes the tissue and kills the cells.

Question 213: What test is used to differentiate maternal from fetal blood?

A. Osmotic fragility test
B. Water bulb test
C. Apt test (Correct Answer)
D. Kleihauer Betke test

Explanation: ### 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.

Question 214: Aneuploidy is the most common genetic abnormality, accounting for up to 50% of clinical miscarriages. All are true about aneuploidy, EXCEPT?

A. 30-40% of fetuses with trisomy 21 die between 12 weeks and 40 weeks gestation.
B. 50-60% of fetuses with trisomy 18 die between 12 weeks and 40 weeks gestation. (Correct Answer)
C. The occurrence of triploidy is not related to the progression of maternal age.
D. In a previous pregnancy with trisomy 21 due to non-disjunction, the risk in a future pregnancy is 0.75% higher.

Explanation: This question tests your knowledge of the natural history and epidemiology of chromosomal abnormalities in pregnancy. **Explanation of the Correct Answer (Option B):** Option B is the incorrect statement (and thus the correct answer) because it underestimates the intrauterine lethality of Trisomy 18 (Edwards Syndrome). In reality, approximately **80%** of fetuses with Trisomy 18 die between 12 weeks of gestation and full term. Trisomy 18 and Trisomy 13 have much higher intrauterine demise rates compared to Trisomy 21. **Analysis of Other Options:** * **Option A:** This is a **true** statement. While Trisomy 21 (Down Syndrome) has the highest survival rate among autosomal trisomies, roughly 30-40% of these fetuses still succumb to intrauterine demise between the end of the first trimester and term. * **Option C:** This is a **true** statement. Unlike autosomal trisomies (13, 18, 21), which are strongly associated with advanced maternal age due to meiotic non-disjunction, **triploidy** (69 chromosomes) is usually a result of diandry (double fertilization of one egg) and is not related to maternal age. * **Option D:** This is a **true** statement. If a previous pregnancy involved a trisomy due to non-disjunction, the recurrence risk in a subsequent pregnancy is approximately **0.75% to 1%** higher than the age-related baseline risk. **High-Yield NEET-PG Pearls:** * **Most common trisomy in miscarriages:** Trisomy 16 (never seen in live births). * **Most common trisomy in live births:** Trisomy 21. * **Most common single chromosomal anomaly in miscarriages:** Turner Syndrome (45, X). * **Aneuploidy** is the leading cause of first-trimester spontaneous abortions (50-60%).

Question 215: A 27-year-old has just had an ectopic pregnancy. Which of the following events would be most likely to predispose to ectopic pregnancy?

A. Previous tubal surgery
B. Pelvic inflammatory disease (PID) (Correct Answer)
C. Use of a contraceptive uterine device (IUD)
D. Induction of ovulation

Explanation: **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.

Question 216: A multigravida with previous 2 normal deliveries presents with unstable lie of the fetus at 34 weeks gestation. What is the most probable cause?

A. Placenta previa (Correct Answer)
B. Oligohydramnios
C. Uterine anomaly
D. Pelvic contracture

Explanation: **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).

Question 217: What is the best method for assessing fetal well-being at term?

A. Serial estriol estimation (Correct Answer)
B. Serial pregnanediol estimation
C. Serial HPL estimation
D. All of the above

Explanation: **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.

Question 218: At which gestational age is the amount of amniotic fluid typically maximum?

A. 32-34 weeks
B. 34-36 weeks (Correct Answer)
C. 36-38 weeks
D. 38-40 weeks

Explanation: 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) < 2 cm defines oligohydramnios, while > 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 219: 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?

A. She should be admitted for an immediate cesarean section
B. She should be admitted for Pitocin induction
C. Schedule a cesarean section in 1 week if she has not undergone spontaneous labor in the meantime
D. Continue to monitor kick counts and return to the office in 1 week to reassess the situation (Correct Answer)

Explanation: **Explanation:** The management of a late-term pregnancy (41 0/7 to 41 6/7 weeks) requires balancing the risks of post-term complications against the risks of failed induction. **Why Option D is Correct:** The patient is currently at **41 weeks** with a **favorable fetal status** (good kick counts) and an **unfavorable cervix** (Bishop score is low: firm, posterior, 1 cm dilated, -1 station). In a healthy G1P0 at 41 weeks with reassuring fetal surveillance, expectant management until 42 0/7 weeks is a standard and acceptable option. While many clinicians offer induction at 41 weeks, the most conservative and correct step in this specific scenario—given the unfavorable cervix and reassuring fetal movement—is to continue monitoring and reassess. **Why Other Options are Incorrect:** * **Option A:** Cesarean section is not indicated for post-date pregnancy alone unless there is fetal distress or a contraindication to vaginal delivery. * **Option B:** While Pitocin induction is an option after 41 weeks, an unfavorable cervix (low Bishop score) in a nulliparous woman significantly increases the risk of a failed induction and subsequent C-section. * **Option C:** Routine elective C-section at 42 weeks is not standard practice; induction of labor is the preferred management if spontaneous labor does not occur by 42 weeks. **Clinical Pearls for NEET-PG:** * **Definitions:** Late-term (41 0/7 – 41 6/7 weeks); Post-term (≥ 42 0/7 weeks). * **Bishop Score:** A score <6 suggests an unfavorable cervix; cervical ripening (e.g., PGE2) is usually required before Pitocin. * **Risks of Post-term Pregnancy:** Macrosomia, Meconium Aspiration Syndrome, Oligohydramnios, and Uteroplacental insufficiency. * **Surveillance:** If expectant management is chosen after 41 weeks, twice-weekly testing (NST + Amniotic Fluid Index/Biophysical Profile) is typically initiated.

Question 220: Which of the following statements is true regarding chorionicity in multifetal pregnancy?

A. Monochorionic membranes should have four layers.
B. Dichorionic pregnancies are always dizygotic.
C. Monochorionic pregnancies are always dizygotic.
D. Chorionicity is accurately determined by first trimester ultrasound scan. (Correct Answer)

Explanation: ### Explanation **1. Why Option D is Correct:** Chorionicity (the number of placentas) is the most critical factor in determining the prognosis and management of multifetal pregnancies. The **first trimester (11–14 weeks)** is the "gold standard" window for determining chorionicity via ultrasound. During this period, the presence of the **Lambda sign** (or Twin Peak sign) indicates a dichorionic pregnancy, while the **T-sign** indicates a monochorionic pregnancy. Accuracy decreases as the pregnancy progresses because the membranes may fuse or thin out. **2. Why the Other Options are Incorrect:** * **Option A:** Monochorionic-diamniotic membranes consist of only **two layers** (amnion-amnion). Dichorionic-diamniotic membranes consist of **four layers** (amnion-chorion-chorion-amnion). * **Option B:** While all dizygotic (fraternal) twins are dichorionic, **dichorionic pregnancies are not always dizygotic**. Approximately 25–30% of monozygotic (identical) twins result from early cleavage (days 1–3) and develop as dichorionic-diamniotic. * **Option C:** Monochorionic pregnancies are **always monozygotic**. They result from the division of a single fertilized ovum between days 4 and 13 post-fertilization. **3. High-Yield Clinical Pearls for NEET-PG:** * **Lambda Sign (Twin Peak):** Pathognomonic for **Dichorionic** twins. * **T-Sign:** Pathognomonic for **Monochorionic** twins. * **Vanishing Twin Syndrome:** More common in dichorionic pregnancies. * **Twin-to-Twin Transfusion Syndrome (TTTS):** Occurs exclusively in **monochorionic** pregnancies due to vascular anastomoses. * **Timing of Cleavage:** * Days 1–3: Dichorionic-Diamniotic (DCDA) * Days 4–8: Monochorionic-Diamniotic (MCDA) — *Most common monozygotic type.* * Days 8–13: Monochorionic-Monoamniotic (MCMA) * >Day 13: Conjoined twins.

Practice by Chapter

Fetal Assessment Techniques

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Hypertensive Disorders in Pregnancy

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Intrauterine Growth Restriction

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Multiple Gestation

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Rh Isoimmunization and Other Blood Group Incompatibilities

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Intrauterine Fetal Therapy

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Prenatal Diagnosis and Genetic Counseling

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Placental Abnormalities

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Preterm Labor and Delivery

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Management of Medical Disorders in Pregnancy

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