Which congenital anomaly is most commonly associated with oligohydramnios?

Which congenital anomaly is most commonly associated with oligohydramnios?

• A. Posterior urethral valves
• B. Anencephaly
• C. Gastroschisis
• D. Hydrops fetalis

Answer: (A)

Oligohydramnios occurs when there is less amniotic fluid, which in the later stages of pregnancy mainly reflects fetal urine production. If there is a urinary tract obstruction, the fetus can’t excrete urine effectively, reducing the amniotic fluid volume. Posterior urethral valves cause a bladder outlet obstruction in male fetuses, leading to decreased urine flow, bladder distention and hydronephrosis, and ultimately low amniotic fluid. This strong link makes this congenital anomaly the most common association with oligohydramnios. Anencephaly, by contrast, often leads to polyhydramnios because the fetus cannot swallow normally. Gastroschisis and hydrops fetalis don’t have as direct or as strong a association with reduced amniotic fluid as urinary obstruction does, so they’re less likely explanations for oligohydramnios.

Oligohydramnios occurs when there is less amniotic fluid, which in the later stages of pregnancy mainly reflects fetal urine production. If there is a urinary tract obstruction, the fetus can’t excrete urine effectively, reducing the amniotic fluid volume. Posterior urethral valves cause a bladder outlet obstruction in male fetuses, leading to decreased urine flow, bladder distention and hydronephrosis, and ultimately low amniotic fluid. This strong link makes this congenital anomaly the most common association with oligohydramnios.

Anencephaly, by contrast, often leads to polyhydramnios because the fetus cannot swallow normally. Gastroschisis and hydrops fetalis don’t have as direct or as strong a association with reduced amniotic fluid as urinary obstruction does, so they’re less likely explanations for oligohydramnios.