Available data suggests that mefloquine is safe and effective for use by pregnant women during all trimesters of pregnancy, and it is widely used for this indication. In pregnant women, mefloquine appears to pose minimal risk to the fetus, and is not associated with increased risk of birth defects or miscarriages. Compared to other malaria chemoprophylaxis regimens, however, mefloqinone may produce more side effects in non-pregnant travelers.
Mefloquine is also safe and effective for use during breastfeeding, though it appears in breast milk in low concentrations. The World Health Organization (WHO) gives approval for the use of mefloquine in the second and third trimesters of pregnancy and use in the first trimester does not mandate termination of pregnancy.