Maternal-Fetal Medicine Practice Questions

Q: A 18-week pregnant multigravida, Rh-negative, with a previous child born with a chromosomal abnormality, underwent cordocentesis. Which test is used to differentiate between maternal and fetal blood in a given sample?

Apt test. **Explanation:** The correct answer is the **Apt test** (Alkali Denaturation Test). This test is specifically designed to differentiate between fetal and maternal blood based on the biochemical properties of hemoglobin. **1. Why the Apt test is correct:** Fetal hemoglobin (**HbF**) is resistant to denaturation by strong bases, whereas adult hemoglobin (**HbA**) is not. In this test, the blood sample is mixed with 1% sodium hydroxide (NaOH). If the blood is maternal (HbA), it denatures and turns **yellow-brown**. If the blood is fetal (HbF), it remains stable and stays **pink**. This is crucial during cordocentesis to ensure the sample obtained is truly fetal blood and not contaminated by maternal blood. **2. Why the other options are incorrect:** * **Kleihauer-Betke test:** This is used to **quantify** the amount of fetal-maternal hemorrhage (FMH) in the maternal circulation (e.g., to calculate the dose of Anti-D). It is an acid-elution test performed on a maternal blood smear, not a direct test to identify the source of a sample. * **Osmotic fragility test:** Used primarily to diagnose **Hereditary Spherocytosis** by measuring the resistance of RBCs to hemolysis in hypotonic solutions. * **Bubble stability test:** A bedside test used to assess **fetal lung maturity** by checking for the presence of surfactants in amniotic fluid. **Clinical Pearls for NEET-PG:** * **Apt Test Uses:** Differentiating fetal from maternal blood in cases of **Vasa Previa** (vaginal bleeding) or during **Cordocentesis**. * **Cordocentesis (PUBS):** Usually performed after 18 weeks; the most common site is the umbilical vein at the placental insertion. * **Kleihauer-Betke Formula:** Fetal cells counted / Total cells × 5000 = Volume of FMH (mL). This is a high-yield calculation for Rh-isoimmunization questions.

Q: In a patient receiving magnesium sulfate therapy, at what serum magnesium level does the patellar (knee) reflex typically disappear?

10-12 mEq/L. ### Explanation Magnesium sulfate ($MgSO_4$) is the drug of choice for seizure prophylaxis in pre-eclampsia and control in eclampsia. It acts as a CNS depressant and neuromuscular blocker. Because it is excreted almost entirely by the kidneys, toxicity is a significant risk, especially in patients with renal impairment. Monitoring clinical signs is vital because they disappear in a predictable, sequential order as serum levels rise. **1. Why Option B is Correct:** The **patellar reflex (knee jerk)** is the first clinical sign of magnesium toxicity. It typically disappears when serum magnesium levels reach **10–12 mEq/L** (or 8–10 mg/dL). This occurs because magnesium inhibits the release of acetylcholine at the neuromuscular junction, blocking the deep tendon reflex arc. **2. Analysis of Incorrect Options:** * **Option A (6–8 mEq/L):** This is the **therapeutic range** required for seizure prophylaxis. At this level, reflexes are present, and the patient is hemodynamically stable. * **Option C (12–14 mEq/L):** At these levels, **respiratory depression** and narcosis occur. This is a critical emergency requiring immediate intervention. * **Option D (>15 mEq/L):** Levels exceeding 15–20 mEq/L lead to **cardiac arrest** due to the direct effect of magnesium on the cardiac conduction system (heart block). **3. Clinical Pearls for NEET-PG:** * **Antidote:** 10 ml of 10% **Calcium Gluconate** IV (administered over 10 minutes). * **Monitoring Parameters:** Before every dose, check for: 1. Presence of patellar reflex (earliest sign of toxicity). 2. Respiratory rate >12–14/min. 3. Urine output >30 ml/hr (as magnesium is renally excreted). * **Therapeutic Level Conversion:** 4–7 mEq/L is approximately 4.8–8.4 mg/dL. Always check the units provided in the question.

Q: A 21-year-old woman with 8 weeks of amenorrhea presents in shock. What is the likely diagnosis?

Ruptured ectopic pregnancy. **Explanation:** The clinical presentation of a young woman with **amenorrhea (8 weeks)** and sudden **hypovolemic shock** is a classic "spotter" for a **Ruptured Ectopic Pregnancy**. In this condition, the gestational sac implants outside the uterine cavity (most commonly in the ampulla of the fallopian tube). As the embryo grows, it outstrips the distensibility of the tube, leading to rupture and massive intraperitoneal hemorrhage, which manifests as shock. **Analysis of Options:** * **Ruptured Ectopic Pregnancy (Correct):** This is the most common cause of life-threatening hemoperitoneum in the first trimester. The 8-week mark is a typical time for tubal rupture. * **Incarcerated Uterus:** This usually occurs between 12–16 weeks of gestation when a retroverted gravid uterus becomes trapped in the pelvic cavity. It presents with urinary retention, not sudden shock. * **Torsion of Ovarian Cyst:** While it causes acute pelvic pain, it rarely leads to hemodynamic collapse (shock) unless accompanied by rupture of a large hemorrhagic cyst or infarction leading to secondary sepsis. * **Threatened Abortion:** This presents with vaginal bleeding and mild cramping with a closed cervical os. It does not cause shock unless it progresses to an Incomplete Abortion with massive external hemorrhage. **NEET-PG High-Yield Pearls:** * **Most common site of Ectopic Pregnancy:** Fallopian tube (95%), specifically the **Ampulla**. * **Most common site for rupture:** Isthmus (6–8 weeks) due to its narrow lumen; Ampulla ruptures later (8–12 weeks). * **Gold Standard Diagnosis:** Laparoscopy. * **Classic Triad:** Amenorrhea, abdominal pain, and vaginal bleeding (present in only 50% of cases). * **Management of Shock:** Immediate aggressive fluid resuscitation and **emergency laparotomy** (salpingectomy) to control bleeding.

Q: What is the recommended treatment for placenta accreta?

Hysterectomy. **Explanation:** **Placenta Accreta** is a life-threatening obstetric complication where the chorionic villi adhere directly to the myometrium due to a partial or total absence of the decidua basalis. **Why Hysterectomy is the Correct Answer:** The gold standard and recommended management for placenta accreta is a **planned cesarean hysterectomy**. Attempting to detach the placenta often leads to massive, uncontrollable postpartum hemorrhage (PPH) because the placenta cannot separate naturally from the uterine wall. To minimize blood loss and maternal morbidity, the uterus is removed with the placenta left *in situ* after the delivery of the fetus. **Analysis of Incorrect Options:** * **A. Manual separation:** This is strictly **contraindicated**. Forcing separation leads to profuse hemorrhage, disseminated intravascular coagulation (DIC), and maternal mortality. * **C. Leave it alone:** While "expectant management" (leaving the placenta to resorb) is an option for women strongly desiring future fertility, it is not the *recommended* primary treatment due to high risks of delayed hemorrhage and severe infection/sepsis. * **D. Hysterectomy and removal of placenta:** This is incorrect because the placenta should **not** be removed prior to or during the hysterectomy. Attempting to remove it first triggers the very bleeding the surgery aims to avoid. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Factors:** Most common risk factors are a **previous Cesarean section** and **Placenta Previa**. * **Spectrum:** Accreta (adheres to myometrium), Increta (invades myometrium), Percreta (penetrates through serosa/into bladder). * **Diagnosis:** Antenatal diagnosis is primarily via **Ultrasound/Doppler** (look for "Swiss cheese" appearance/placental lacunae and loss of retroplacental hypoechoic zone). * **Management:** If diagnosed antenatally, the surgery is ideally scheduled at **34 0/7–35 6/7 weeks** of gestation.

Q: A 25-year-old female presents to the casualty with a history of amenorrhea for two and a half months and abdominal pain and bleeding per vaginum for one day. On examination, vital parameters and other systems are normal. On speculum examination, bleeding is found to come from the Os. On bimanual examination, the uterus is of 10 weeks size, soft, and the Os admits one finger. What is the most likely diagnosis?

Inevitable abortion. **Explanation:** The clinical presentation of amenorrhea, vaginal bleeding, and abdominal pain in the first trimester suggests a spontaneous abortion. The definitive diagnostic feature in this case is the **dilated internal cervical os** (admits one finger) in the presence of vaginal bleeding. 1. **Inevitable Abortion (Correct):** This is defined as a clinical state where the pregnancy is complicated by vaginal bleeding and abdominal pain, and the **internal os is open**, making the continuation of pregnancy impossible. The uterine size usually corresponds to the period of amenorrhea (10 weeks in this case). 2. **Threatened Abortion (Incorrect):** While bleeding and pain are present, the hallmark of threatened abortion is a **closed internal os**. The pregnancy is potentially viable. 3. **Missed Abortion (Incorrect):** This refers to the retention of a dead fetus in utero for several weeks. Typically, the **internal os is closed**, and the uterine size is **smaller** than the period of amenorrhea. 4. **Incomplete Abortion (Incorrect):** In this condition, some products of conception have been expelled while some remain. The **os is open**, but the uterine size is typically **smaller** than the period of amenorrhea due to partial evacuation. **High-Yield Clinical Pearls for NEET-PG:** * **Os Status is Key:** If the Os is **Closed**, it is either Threatened, Missed, or Complete abortion. If the Os is **Open**, it is either Inevitable or Incomplete abortion. * **Management of Inevitable Abortion:** If 12 weeks, uterine contraction is induced via Oxytocin or Prostaglandins. * **Uterine Size:** In Inevitable abortion, Uterine Size = Period of Amenorrhea. In Incomplete/Missed abortion, Uterine Size < Period of Amenorrhea.

Question 1

Which one of the following regarding antenatal assessment of umbilical arteries by color Doppler study is TRUE?

Accepted Answer

The flow velocities and the S/D ratio are useful to evaluate high-risk pregnancies

Answer

There is decreased S/D ratio in smoker and nicotine abusing pregnant females

Answer

The reduced diastolic flow at term indicates good prognosis

Answer

In otherwise normal pregnancies, the increased S/D ratio is normal in smoking females

Question 2

A 18-week pregnant multigravida, Rh-negative, with a previous child born with a chromosomal abnormality, underwent cordocentesis. Which test is used to differentiate between maternal and fetal blood in a given sample?

Accepted Answer

Apt test

Answer

Kleihauer-Betke test

Answer

Osmotic fragility test

Answer

Bubble stability test

Question 3

Regarding trophoblast invasion of maternal spiral arteries, all are true except?

Accepted Answer

Invasion by trophoblasts involves both decidual spiral arteries and decidual veins.

Answer

First wave occurs before 12 weeks and consists of invasion up to the border between decidua and myometrium.

Answer

Second wave occurs between 12 and 16 weeks with invasion of intramyometrial segments of spiral arteries.

Answer

Narrow lumen, muscular spiral arteries are converted into dilated, low resistance vessels.

Question 4

In a patient receiving magnesium sulfate therapy, at what serum magnesium level does the patellar (knee) reflex typically disappear?

Accepted Answer

10-12 mEq/L

Answer

6-8 mEq/L

Answer

12-14 mEq/L

Answer

Greater than 15 mEq/L

Question 5

Which of the following is true about chorionic villi biopsy?

Accepted Answer

Rh immunoglobulin prophylaxis is not necessary

Answer

Strongly associated with fetal limb defects

Answer

Done between 10-12 weeks of gestation

Answer

Done to diagnose genetic disorders

Question 6

A 21-year-old woman with 8 weeks of amenorrhea presents in shock. What is the likely diagnosis?

Accepted Answer

Ruptured ectopic pregnancy

Answer

Incarcerated amnion

Answer

Torsion of ovarian cyst

Answer

Threatened abortion

Question 7

In peripartum cardiomyopathy, cardiac failure can develop anytime during which period?

Accepted Answer

The last month of pregnancy or within 5 months after delivery

Answer

The antenatal period

Answer

The third trimester

Answer

The first 6 weeks postpartum

Question 8

What is the recommended treatment for placenta accreta?

Accepted Answer

Hysterectomy

Answer

Manual separation

Answer

Leave it alone

Answer

Hysterectomy and removal of placenta

Question 9

Cesarean delivery is mandatory in which of the following types of placenta previa?

Accepted Answer

Type 3

Answer

Type 1

Answer

Type 2

Answer

All of the above

Question 10

A 25-year-old female presents to the casualty with a history of amenorrhea for two and a half months and abdominal pain and bleeding per vaginum for one day. On examination, vital parameters and other systems are normal. On speculum examination, bleeding is found to come from the Os. On bimanual examination, the uterus is of 10 weeks size, soft, and the Os admits one finger. What is the most likely diagnosis?

Accepted Answer

Inevitable abortion

Answer

Threatened abortion

Answer

Missed abortion

Answer

Incomplete abortion

Maternal-Fetal Medicine — MCQs

Maternal-Fetal Medicine — MCQs

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