Critical Periods of Neuroendocrine Development: Effects of Prenatal Xenobiotics

It is now generally accepted that the developing fetus may be adversely affected by exposure to drugs and environmental chemicals. The stage of development of the intrauterine host is a major determinant of the resultant drug or chemical action. With rare exception, all foreign compounds are transmitted across the placenta, and depending upon their solubility and chemical structure, achieve varying concentrations in the fetus. Historically, the concept that external agents could adversely effect the fetus was first expounded by Gregg1 in Australia nearly 50 years ago when he demonstrated that rubella infection in the mother could lead to congenital cataracts in the newborn infant. During the several decades following Gregg’s report, most concern regarding drug effects on the fetus had to do with the perinatal period, particularly with the effect of narcotics and analgesics on the ability of the newborn infant to sustain respiration following delivery.