Which analgesic is generally avoided in the third trimester?

• A. NSAIDs
• B. Acetaminophen
• C. Ibuprofen
• D. Opioids

Answer: (A)

In late pregnancy, drugs that block prostaglandin synthesis can disrupt fetal circulation. NSAIDs inhibit COX enzymes, lowering prostaglandin levels and causing the ductus arteriosus to close prematurely. The ductus arteriosus is a vital vessel that keeps fetal blood flowing appropriately; premature closure can lead to fetal distress, pulmonary hypertension, and heart strain. NSAIDs can also reduce fetal kidney blood flow, decreasing urine production and leading to oligohydramnios, which can affect fetal lung development and overall growth. For these reasons, NSAIDs are generally avoided in the third trimester.

Acetaminophen is typically considered safe for pain relief during pregnancy and does not carry the same risk to the ductus arteriosus. Ibuprofen is an NSAID, so it shares the same concerns in the third trimester. Opioids may be used if needed, but they carry risks of neonatal respiratory depression and potential withdrawal with prolonged exposure, so they’re used with caution and under supervision.