A time to be born: implications of animal studies in maternal-fetal medicine.

Recent studies on the capabilities of the fetus in the last third of gestation demonstrated that the fetus actively prepares for its journey to the extrauterine environment. The most remarkable of these preparations is that the fetal brain gives the signal to begin the birth process. Several studies, particularly those conducted in sheep, showed that endocrine signals from the fetal brain are sent to the placenta to stimulate increased estrogen production. The increased estrogen production initiates uterine contractility, and starts the labor process. The mother's oxytocin production also plays a role by determining the precise time of the day that the baby is born. These studies produced fascinating insights into fetal and uterine physiology that have already begun to be employed in clinical care. One primary example in the application of this new knowledge obtained originally from studies on fetal sheep is in understanding the endocrine regulation of fetal production of surfactant to treat women in preterm labor and to produce artificial surfactants for the treatment of babies delivered too early. It is important to obtain and use reproducible data gained from carefully controlled animal experiments to rationalize clinical management practices. Basic research should precede changes in clinical management, rather than follow them, as is so often the case.