As public health professionals respond to emerging infections, particular attention needs to be paid to pregnant women and their offspring. Pregnant women might be more susceptible to, or more severely affected by, emerging infections. The effects of a new maternal infection on the embryo or fetus are difficult to predict. Some medications recommended for prophylaxis or treatment could harm the embryo or fetus. We discuss the challenges of responding to emerging infections among pregnant women, and we propose strategies for overcoming these challenges.