Indomethacin is contraindicated after how many weeks of gestation due to the risk of premature closure of the fetal ductus arteriosus?

• A. 28 weeks
• B. 32 weeks
• C. 34 weeks
• D. 38 weeks

Answer: (C)

Indomethacin works by blocking prostaglandin synthesis, and prostaglandins keep the fetal ductus arteriosus open. As pregnancy advances, the ductus becomes more dependent on prostaglandins to stay patent, so inhibiting them late in gestation can cause premature constriction or closure. If the ductus closes before birth, it can reduce blood flow to the lungs and strain the fetal heart, leading to potential fetal compromise. Because of this risk, indomethacin is avoided after about 34 weeks of gestation.