Identify a potential adverse effect of NSAIDs in pregnancy.

The potential adverse effect of NSAIDs (non-steroidal anti-inflammatory drugs) in pregnancy is the premature closure of the ductus arteriosus in the fetus. The ductus arteriosus is a vital blood vessel in the fetal circulation that allows blood to bypass the lungs, which are not yet functioning. Normally, this vessel closes shortly after birth when the newborn begins to breathe air. However, the use of NSAIDs, particularly in the third trimester of pregnancy, can lead to constriction of the ductus arteriosus, potentially resulting in significant complications for the fetus such as pulmonary hypertension or heart failure.

This risk is due to NSAIDs inhibiting the production of prostaglandins, which are necessary for maintaining the patency of the ductus arteriosus. Thus, the timing of NSAID administration and the gestational age of the fetus are crucial factors when considering the safety of these medications during pregnancy.