A woman presents to you at 36 weeks of gestation with complaints of breathlessness and excessive abdominal distension. Fetal movements are normal. On examination, fetal parts are not easily felt and fetal heartbeat is heard but it is muffled. Her symphysis fundal height is 41 cm. Her abdomen is tense but not tender. What is the most likely diagnosis?

Correct Answer: C. Polyhydramnios

Polyhydramnios is the excessive accumulation of amniotic fluid (>2000 mL or AFI >25 cm). This case presents the classic clinical triad: (1) disproportionate uterine enlargement — symphysis-fundal height of 41 cm at 36 weeks (normal ~36 cm) with excessive abdominal distension; (2) maternal respiratory symptoms — breathlessness due to upward displacement of the diaphragm and compression of the lungs; and (3) difficulty palpating fetal parts and muffled fetal heart sounds — because the fetus is "floating" in excess fluid, making clinical examination difficult. The tense, non-tender abdomen reflects fluid tension rather than placental abruption (which causes tenderness and pain). Fetal movements remain normal because the fetus is not compromised. In Indian obstetric practice (per FOGSI guidelines), polyhydramnios is confirmed by ultrasound showing AFI >25 cm or single deepest pocket >10 cm. This is a common examination finding in NEET PG because it tests integration of clinical signs with pathophysiology — the key discriminator is the muffled heart sounds and difficulty feeling fetal parts in the context of excessive uterine size, which is pathognomonic for polyhydramnios.

Why the other options are wrong

A. Abruptio placenta — Abruptio placenta (placental abruption) presents with sudden onset of severe abdominal pain, vaginal bleeding, and a tender, rigid, board-like abdomen — none of which are present here. The patient has a tense but non-tender abdomen. Abruption causes acute fetal distress (abnormal fetal movements or absent heart sounds), not normal fetal movements. The excessive uterine size and muffled heart sounds are not features of abruption. B. Hydrocephalus of fetus — Fetal hydrocephalus causes localized enlargement of the fetal head, not disproportionate uterine enlargement relative to gestational age. While it may increase AFI secondarily, the symphysis-fundal height would not be as markedly elevated (41 cm at 36 weeks). Hydrocephalus is diagnosed on ultrasound by ventricular dilatation (lateral ventricle >10 mm), not by clinical examination findings of muffled heart sounds and difficulty palpating fetal parts. D. Fetal-maternal ascites — Fetal-maternal ascites is an extremely rare condition and would present with signs of fetal hydrops (skin edema, hepatosplenomegaly on ultrasound), not isolated abdominal distension with normal fetal movements. This diagnosis is not supported by the clinical presentation and is not a standard differential in Indian obstetric teaching. The normal fetal movements and muffled (not absent) heart sounds rule out severe fetal compromise.

High-Yield Facts

Mnemonics

POLYHYDRAMNIOS Clinical Signs (FLOAT) Fetal parts hard to feel | Low fetal heart sounds (muffled) | Over-distended abdomen (tense) | Acute breathlessness (maternal) | Tall symphysis-fundal height (disproportionate) Polyhydramnios vs Abruption (PAIN rule) Pain (absent in polyhydramnios, severe in abruption) | Abdomen (tense but soft in polyhydramnios, rigid in abruption) | Increased size (yes in polyhydramnios, no in abruption) | Normal fetal movements (yes in polyhydramnios, abnormal in abruption)

NBE Trap

NBE pairs excessive uterine size with maternal breathlessness to lure students into thinking of abruptio placenta (which causes pain and tenderness) or fetal hydrocephalus (which causes localized head enlargement, not disproportionate uterine size). The key discriminator is the non-tender, tense abdomen with muffled heart sounds — classic for polyhydramnios, not abruption.

Clinical Pearl

In Indian obstetric practice, polyhydramnios is often first suspected clinically when a pregnant woman complains of breathlessness out of proportion to her gestational age and the uterus feels "too big" for dates. Always confirm with ultrasound AFI measurement and screen for maternal diabetes (most common cause in India) and fetal anomalies. Early recognition prevents complications like preterm labor and cord prolapse at delivery.

_Reference: DC Dutta's Textbook of Obstetrics, 8th ed., Ch. 23 (Abnormalities of Amniotic Fluid); FOGSI Clinical Practice Guidelines on Polyhydramnios_