Women who are pregnant, thinking of becoming pregnant or breastfeeding should not use antidiarrheals without first consulting a physician. Salicylates such as bismuth subsalicylate have not been shown to cause birth defects in humans, but are known to cause birth defects in animals. In addition, studies have shown that use of salicylates late in pregnancy may have undesirable effects on a newborn infant’s heart or blood flow. Use of salicylates during the final two weeks of pregnancy may cause bleeding problems in the fetus before or during delivery, whereas excessive use of salicylates during the last three months of pregnancy may result in a variety of problems for the mother. These include extended pregnancy, prolonged labor and severe bleeding before, during or following delivery.

It is not known how loperamide might affect pregnant women and their babies, although animal studies have not shown the drug to cause birth defects.