Medication use in pregnancy is common: 50% to 80% of pregnant women in the US use prescription medications. However, because pregnant women are generally excluded from clinical trials of new medications, little is known about their safety during pregnancy at the time of approval. During the postmarketing period, as pregnant women start using the medication, signals of potential safety risks may emerge. In some instances, the risks are clearly incompatible with use of the medication during pregnancy (eg, thalidomide). However, more commonly, signals of risk emerge that are relatively weak and for outcomes that are relatively rare, creating a challenging situation for patients, prescribers, and regulators. On one hand, there is a desire to avoid using any medication during pregnancy that might have an adverse effect on the developing fetus or the mother. On the other hand, there is often a need to treat medical issues that complicate pregnancy. Regulators, in particular, face a challenge when weak signals of risk emerge given their mandate to protect the public health and prevent the unsafe use of medication. They have to decide how to react to the new information, communicate the risk, and inform clinical practice in a way that mitigates the risk while safeguarding treatment access for women for whom the benefits outweigh the risks.