Every woman should be thinking about her health whether she is planning a pregnancy. One reason is that about half of all pregnancies are not planned. Unplanned pregnancies are at greater risk of preterm birth and low birth weight babies. Another reason is that, despite important advances in medicine and prenatal care, about 1 in 8 babies are born too early. Researchers are trying to find out why and how to prevent preterm birth. But experts agree that women need to be healthier before becoming pregnant. By acting on health issues and risks before pregnancy, you can prevent problems that might affect you or your baby later.