Maternal-Fetal Medicine Practice Questions

Q: You have initiated magnesium sulfate therapy for a patient with eclampsia. Later you notice the respiratory rate is 6/minute and the tendon reflexes are not elicitable. What is the next appropriate step?

Administer calcium gluconate 10 ml over 10 minutes. ### Explanation This clinical scenario describes **Magnesium Sulfate ($MgSO_4$) toxicity**. $MgSO_4$ is the drug of choice for controlling seizures in eclampsia, but it has a narrow therapeutic index. **1. Why Option B is Correct:** The patient is exhibiting classic signs of magnesium toxicity: **loss of deep tendon reflexes (patellar reflex)**, which occurs at serum levels of 7–10 mEq/L, and **respiratory depression** (RR 12 mEq/L. * **Mechanism:** Magnesium acts as a calcium antagonist at the neuromuscular junction. * **Antidote:** **10 ml of 10% Calcium Gluconate** administered IV over 10 minutes is the immediate treatment. Calcium antagonizes the membrane effects of magnesium, reversing respiratory depression and cardiac toxicity. **2. Why Other Options are Incorrect:** * **Option A (Naloxone):** This is an opioid antagonist used for opioid overdose. It has no role in reversing magnesium-induced neuromuscular blockade. * **Option C (Atropine):** This is an anticholinergic used for symptomatic bradycardia or organophosphate poisoning. It does not counteract magnesium. * **Option D (Sodium Bicarbonate):** Used for metabolic acidosis or specific toxicities (like TCAs), but not for $MgSO_4$ toxicity. **3. High-Yield Clinical Pearls for NEET-PG:** * **Monitoring $MgSO_4$:** Always check three parameters before every dose: 1. **Patellar Reflex:** Must be present (First sign of toxicity is loss of reflex). 2. **Respiratory Rate:** Must be >12–14/min. 3. **Urine Output:** Must be >30 ml/hr or >100 ml/4hr (Magnesium is excreted solely by kidneys). * **Therapeutic Range:** 4–7 mEq/L. * **Sequence of Toxicity:** Loss of reflexes $\rightarrow$ Respiratory depression $\rightarrow$ Cardiac arrest (>25 mEq/L). * **Pritchard Regimen:** 4g IV + 10g IM (loading), followed by 5g IM every 4 hours (maintenance).

Q: A woman has had two previous anencephalic babies. What is the risk of having a third one?

10%. **Explanation:** Neural Tube Defects (NTDs), such as anencephaly and spina bifida, follow a **multifactorial inheritance** pattern. This means they result from a combination of multiple genetic predispositions and environmental factors (like folic acid deficiency). In multifactorial inheritance, the recurrence risk increases significantly with each previously affected sibling. * **Why 10% is correct:** In the general population, the risk of NTD is approximately 0.1–0.2%. After **one** affected child, the recurrence risk rises to **2–5%**. After **two** affected children, the risk increases further to approximately **10%**. This is a classic high-yield statistic for postgraduate exams. **Analysis of Incorrect Options:** * **0%:** Incorrect, as genetic and environmental predispositions persist in subsequent pregnancies. * **25%:** This risk is characteristic of **Autosomal Recessive** disorders (e.g., Thalassemia). While some rare syndromes involving NTDs exist, isolated anencephaly does not follow this pattern. * **50%:** This risk is characteristic of **Autosomal Dominant** disorders (if one parent is affected). **Clinical Pearls for NEET-PG:** 1. **Prevention:** For a woman with a previous history of NTD, the recommended dose of **Folic Acid is 4 mg/day**, started at least 1 month (ideally 3 months) prior to conception and continued through the first trimester. 2. **Low-risk prophylaxis:** For women without a history, the standard dose is **400 mcg (0.4 mg)/day**. 3. **Screening:** Maternal Serum Alpha-Fetoprotein (MSAFP) is elevated in open NTDs. Diagnosis is confirmed via targeted ultrasound (Level II scan) at 18–20 weeks.

Q: The fetus, which is foreign to the mother, is not rejected due to which of the following reasons?

All of the above. The survival of the fetus (a semi-allograft) within the maternal environment is a phenomenon known as **immunological privilege**. This is achieved through a multi-factorial mechanism involving anatomical, hormonal, and cellular barriers. ### **Explanation of Options:** * **A. Immunosuppressive effect of placental hormones:** High local concentrations of **Progesterone** and **hCG** at the maternal-fetal interface suppress maternal T-cell activity and promote a shift from a pro-inflammatory (Th1) to an anti-inflammatory (**Th2**) cytokine profile. * **B. Absence of HLA molecules in villous trophoblast:** The syncytiotrophoblast (which is in direct contact with maternal blood) does not express classical **HLA Class I (A, B)** or **Class II** molecules. This prevents recognition and destruction by maternal cytotoxic T-cells. Instead, they express **HLA-G**, which inhibits Natural Killer (NK) cell activity. * **C. Production of blocking antibodies:** Maternal B-cells produce non-complement-fixing antibodies (asymmetric IgG) that bind to fetal antigens, "masking" them from maternal immune recognition without causing damage. ### **Clinical Pearls for NEET-PG:** * **The Th2 Shift:** Pregnancy is a Th2-dominant state. This explains why Th1-mediated autoimmune diseases (like Rheumatoid Arthritis) often improve during pregnancy, while Th2-mediated ones (like SLE) may flare. * **HLA-G:** This is a non-classical Class I MHC molecule unique to the extravillous trophoblast. It is the "shield" that protects the fetus from NK cell-mediated lysis. * **Indoleamine 2,3-dioxygenase (IDO):** An enzyme produced by the placenta that depletes tryptophan, effectively "starving" and inactivating maternal T-cells. * **Fas-L Expression:** Trophoblasts express Fas-ligand, which induces apoptosis in any maternal activated T-cells that attempt to attack the placenta.

Q: Which of the following is true regarding early deceleration in a cardiotocography (CTG)?

It is due to increased vagal tone in the fetus.. ### Explanation **1. Why Option A is Correct:** Early decelerations are characterized by a gradual decrease and return of the fetal heart rate (FHR) that coincides with the peak of a uterine contraction (the "mirror image" pattern). The underlying mechanism is **fetal head compression**. When the fetal head is compressed during a contraction, it leads to an increase in intracranial pressure, which stimulates the **vagus nerve**. This increased vagal tone results in a transient slowing of the heart rate. Because it is a physiological reflex rather than a sign of distress, early decelerations are considered benign. **2. Why the Other Options are Incorrect:** * **Option B (Fetal Hypoxia):** This is associated with **Late Decelerations**. Late decelerations occur due to uteroplacental insufficiency, where reduced blood flow during contractions leads to fetal hypoxia and metabolic acidosis. * **Option C (Raised Maternal BP):** Maternal hypertension (e.g., Preeclampsia) is a risk factor for uteroplacental insufficiency, which would more likely cause *late* decelerations, not early ones. * **Option D (Cord Compression):** This is the hallmark cause of **Variable Decelerations**. These are abrupt in onset and vary in shape and timing relative to contractions. **3. High-Yield Clinical Pearls for NEET-PG:** * **Early Deceleration:** "Mirror image" of contraction; Nadir of FHR matches Peak of contraction; Cause: **Head compression** (Vagal). * **Late Deceleration:** Nadir of FHR occurs *after* the peak of contraction; Cause: **Uteroplacental insufficiency** (Hypoxia). * **Variable Deceleration:** Most common type; V-shaped; Cause: **Umbilical cord compression**. * **Sinusoidal Pattern:** Associated with severe **fetal anemia** (e.g., Rh isoimmunization) or fetal hemorrhage. * **Management:** Early decelerations require no active intervention; they are not indicative of fetal compromise.

Q: Which of the following is NOT a fetal heart tracing finding in maternal carbon monoxide poisoning?

Marked beat-to-beat variability. **Explanation:** Maternal carbon monoxide (CO) poisoning leads to fetal hypoxia through two primary mechanisms: the formation of **carboxyhemoglobin (COHb)**, which reduces the oxygen-carrying capacity of blood, and a **leftward shift of the oxyhemoglobin dissociation curve**, which prevents the release of oxygen to fetal tissues. **Why "Marked beat-to-beat variability" is the correct answer:** Fetal hypoxia typically leads to a **depression** of the fetal central nervous system (CNS). In cases of CO poisoning, the resulting hypoxia and acidosis cause a **decrease** in variability, not an increase. Marked (saltatory) variability is usually associated with acute umbilical cord compression or early hypoxia, but it is not a characteristic finding of the profound, systemic cellular hypoxia caused by CO poisoning. **Analysis of incorrect options:** * **Elevated baseline (Tachycardia):** This is an early compensatory response to fetal hypoxia as the fetus attempts to increase cardiac output to maintain tissue perfusion. * **Absence of accelerations:** Accelerations signify a healthy, reactive CNS. In CO poisoning, the hypoxic state leads to a non-reactive stress test (NST). * **Decreased beat-to-beat variability:** This is a hallmark finding of fetal acidemia and CNS depression resulting from prolonged or severe CO exposure. **Clinical Pearls for NEET-PG:** * **Affinity:** CO has an affinity for hemoglobin **200–250 times** greater than oxygen. * **Fetal Impact:** Fetal COHb levels are typically **10–15% higher** than maternal levels because fetal hemoglobin has an even higher affinity for CO, and clearance is slower. * **Treatment:** The definitive treatment is **100% normobaric oxygen** for the mother. Hyperbaric oxygen (HBO) is indicated if the mother is unconscious, has neurological symptoms, or has a COHb level >20%.

Q: Absent stomach bubble on antenatal ultrasonography is an important finding for the antenatal diagnosis of?

Esophageal atresia in the fetus. **Explanation:** The presence of a fluid-filled **stomach bubble** on antenatal ultrasonography is a marker of a functional upper gastrointestinal tract. Fetal swallowing of amniotic fluid begins around 10–12 weeks; this fluid then passes through the esophagus into the stomach. **1. Why Esophageal Atresia is correct:** In **Esophageal Atresia (EA)**, there is a physical discontinuity of the esophagus. If there is no distal tracheoesophageal fistula (TEF), or if the fistula is too narrow, the swallowed amniotic fluid cannot reach the stomach. This results in an **absent or persistently small stomach bubble**. This finding is often associated with **polyhydramnios**, as the fetus cannot effectively recirculate amniotic fluid. Note: In 90% of cases (Type C EA with distal TEF), a small stomach bubble may still be seen due to air/fluid entering from the trachea. **2. Why other options are incorrect:** * **Congenital heart disease:** Typically diagnosed via fetal echocardiography (e.g., four-chamber view abnormalities). It does not directly affect the presence of the stomach bubble. * **Omphalocele:** This is a ventral wall defect where bowel loops (and sometimes the liver) herniate into the umbilical cord. While the stomach may be displaced into the sac, it is usually visible. * **Spina bifida:** A neural tube defect diagnosed by visualizing spinal dysraphism or cranial signs (Lemon/Banana signs). It does not interfere with swallowing. **Clinical Pearls for NEET-PG:** * **Differential Diagnosis for Absent Stomach Bubble:** Esophageal atresia, diaphragmatic hernia (stomach moved into the chest), facial clefts/masses (inability to swallow), or neuromuscular disorders. * **VACTERL Association:** Always screen for Vertebral, Anal, Cardiac, TEF, Renal, and Limb anomalies when EA is suspected. * **Double Bubble Sign:** Distinct from "absent bubble," this indicates **Duodenal Atresia**.

Q: Which of these is the function of Decidua basalis of the endometrium?

Formation of placenta. **Explanation:** The **Decidua** is the modified functional layer of the endometrium during pregnancy, transformed under the influence of progesterone (decidualization). It is divided into three distinct regions based on its anatomical relationship to the implanted embryo: 1. **Decidua Basalis (Correct Answer):** This is the part of the decidua located directly deep to the conceptus (at the site of implantation). It interacts with the fetal chorion frondosum to form the **maternal component of the placenta**. It provides the vascular environment necessary for nutrient and gas exchange. 2. **Decidua Capsularis:** The portion that covers the blastocyst, separating it from the uterine cavity. 3. **Decidua Parietalis:** The remainder of the endometrium lining the rest of the uterine cavity. **Analysis of Incorrect Options:** * **Options A & D:** These describe the cyclical changes of the **functional layer** of the endometrium during a non-pregnant menstrual cycle (Proliferative phase under Estrogen and Secretory phase under Progesterone). Once pregnancy occurs, these changes transition into decidualization. * **Option C:** Shedding during the menstrual phase involves the *Stratum Functionale*. In pregnancy, the decidua is maintained to support the fetus and is only shed after parturition (childbirth). **High-Yield NEET-PG Pearls:** * **Nitabuch’s Layer:** A fibrinoid layer between the decidua basalis and the cytotrophoblast that prevents over-invasion of the placenta. Absence of this layer leads to **Placenta Accreta**. * **Arias-Stella Reaction:** Hypersecretory changes in endometrial glands (enlarged nuclei) seen in pregnancy; it can be mistaken for malignancy but is a normal response to HCG. * The **Chorion Frondosum** (fetal part) + **Decidua Basalis** (maternal part) = **The Placenta**.

Question 1

For diagnosing chronic hypertension in pregnancy, hypertension is considered present prior to what gestational age?

Accepted Answer

20 weeks

Answer

8 weeks

Answer

14 weeks

Answer

24 weeks

Question 2

A 28-year-old woman (Gravida 2, Para 1, Abortus 0) at 36 weeks of gestation has a history of a prior stillbirth at 37 weeks. What is the optimal timing for delivery in this current pregnancy?

Accepted Answer

39 weeks of gestation

Answer

Immediately

Answer

37 weeks of gestation

Answer

38 weeks of gestation

Question 3

You have initiated magnesium sulfate therapy for a patient with eclampsia. Later you notice the respiratory rate is 6/minute and the tendon reflexes are not elicitable. What is the next appropriate step?

Accepted Answer

Administer calcium gluconate 10 ml over 10 minutes

Answer

Administer naloxone at 0.01 mg/kg over 5 minutes

Answer

Administer 0.4 mg atropine IV

Answer

Administer 5 mEq/kg sodium bicarbonate IV over 10 minutes

Question 4

A woman has had two previous anencephalic babies. What is the risk of having a third one?

Accepted Answer

10%

Answer

0%

Answer

25%

Answer

50%

Question 5

The fetus, which is foreign to the mother, is not rejected due to which of the following reasons?

Accepted Answer

All of the above

Answer

Immunosuppressive effect of placental hormones

Answer

Absence of HLA molecules in villous trophoblast

Answer

Production of blocking antibodies

Question 6

Which of the following is true regarding early deceleration in a cardiotocography (CTG)?

Accepted Answer

It is due to increased vagal tone in the fetus.

Answer

It is due to fetal hypoxia.

Answer

It is due to raised blood pressure in the mother.

Answer

It is due to cord compression.

Question 7

Which of the following is NOT a fetal heart tracing finding in maternal carbon monoxide poisoning?

Accepted Answer

Marked beat-to-beat variability

Answer

Elevated baseline

Answer

Absence of accelerations

Answer

Decreased beat-to-beat variability

Question 8

Absent stomach bubble on antenatal ultrasonography is an important finding for the antenatal diagnosis of?

Accepted Answer

Esophageal atresia in the fetus

Answer

Congenital heart disease in the fetus

Answer

Omphalocele in the fetus

Answer

Spina bifida in the fetus

Question 9

Which of these is the function of Decidua basalis of the endometrium?

Accepted Answer

Formation of placenta

Answer

Monthly proliferation in response to estrogen

Answer

Shedding during menstrual phase

Answer

Secretory changes in response to progesterone

Question 10

Which of the following statements is true regarding Acute Fatty Liver of Pregnancy?

Accepted Answer

Occurs due to LCHAD deficiency (long-chain 3-hydroxyacyl coenzyme A dehydrogenase)

Answer

Characterized by macrovesicular steatosis with periportal sparing

Answer

Associated with an increase in fibrinogen, ammonia, and SGOT

Answer

Most cases are asymptomatic

Maternal-Fetal Medicine — MCQs

Maternal-Fetal Medicine — MCQs

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