Which medication is a prostaglandin inhibitor used to reduce preterm labor risk?

• A. Indomethacin
• B. Nifedipine
• C. Terbutaline
• D. Magnesium sulfate

Answer: (A)

Prostaglandins drive uterine contractions and help cervical ripening, so lowering prostaglandin production can reduce preterm labor risk. Indomethacin is an NSAID that inhibits cyclooxygenase, which decreases prostaglandin synthesis and thereby reduces myometrial activity to help delay preterm labor, especially when used earlier in pregnancy. The other options work through different mechanisms: a calcium channel blocker lowers intracellular calcium in smooth muscle to promote relaxation; a beta-agonist increases cAMP to relax the uterus; magnesium sulfate acts as a smooth muscle relaxant and neuroprotectant with a calcium-related effect. Indomethacin is favored here because its primary action is prostaglandin inhibition, aligning with the goal of suppressing prostaglandin-driven contractions. Caution is needed with this drug due to risks like premature ductus arteriosus closure and oligohydramnios if used later in pregnancy or for too long.