Fetal breathing movements. An update for the pediatrician.

Although the presence of fetal breathing movements (FBMs) has been suspected for almost a century, the major advances in the field were made during the last decade. Experimental animal techniques of detection include instrumentation of fetuses with electronic recording equipment. Human studies use more indirect, although no less accurate, A-mode or real-time B-scan ultrasonography in the recording of FBMs. The fetus does not make breathing movements continuously; however, there are periods of FBMs interspersed with periods of apnea. Inherent to FBMs is a diurnal variation. Hypoxia and hypoglycemia diminish FBMs, while hypercarbia and hyperglycemia have the opposite effect. Caffeine, barbiturates, and general anesthetics modify FBMs by their influence on the CNS. Preliminary studies have shown the presence of FBMs to indicate a state of fetal well-being. Possibly, in the future, testing for FBMs may become a useful clinical tool in the identification of the fetus at risk.