FRIDAY, Dec. 4 (HealthDay News) -- The use of beta 2 adrenergic agonist medications in pregnancy can disrupt the fetus's sympathetic and parasympathetic nervous system activity, possibly resulting in autism spectrum disorders, poor cognition, impaired motor function, psychiatric problems, high blood pressure and poor school performance, according to a review published in the December issue of the American Journal of Obstetrics & Gynecology.

Frank R. Witter, M.D., of Johns Hopkins University in Baltimore, and colleagues reviewed the basic science and the animal and human research on the effects on the fetus of the use of beta 2 adrenergic agonist drugs in pregnancy, such as terbutaline for preterm labor and albuterol for asthma.

The research suggests that the drugs can cause beta 2 adrenergic receptor over-stimulation during critical prenatal development causing a permanent shift in the fetus's sympathetic-to-parasympathetic tone, which leads to functional and behavioral teratogenesis. The peak risk is the mid-to-late second trimester through the early third trimester, during which time peak brain development occurs. Risk for autism increases with continuous high-dose exposure for more than two weeks. Some fetuses may be more genetically susceptible than others to the disruptive effect.

"Given the risk of long-term neurophysiologic and behavioral impairment, the use of beta 2 adrenergic agonists should be limited to proven indications when alternate drugs are ineffective or unavailable and when the risks of the untreated disease to the mother and fetus are greater than the risk of the beta 2 adrenergic agonist," the authors write.

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