The role of basic science in preventing low birth weight.

Recent experimental studies in a wide range of animal species have shown that the fetus determines the duration of pregnancy. The mechanism by which the birth process is initiated is closely linked to the normal maturation of vital fetal organs, such as the lungs. Thus, under normal circumstances, the fetus should be adequately prepared for the challenges of an independent life after birth. The fetal endocrine changes that lead to birth result in increased maternal estrogen production and stimulation of effective uterine contractility and dilation of the cervix. Preterm delivery can occur as a result of several different pathological processes, including infection and various forms of stress. Successful strategies for preventing the preterm delivery of low birth weight infants will depend upon an improved ability to diagnose which of the many components of the normal birth process has been prematurely activated in each pregnant patient undergoing premature labor.