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Prenatal use of erythromycin does not appear to increase the risk of infantile hypertrophic pyloric stenosis

A woman's use of the antibiotic erythromycin during pregnancy does not appear to increase her infant's risk of developing infantile hypertrophic pyloric stenosis (IHPS), a condition that results in gastric outlet obstruction and requires surgery. Erythromycin is believed to interact with motilin receptors in the stomach, present in the fetus beginning at 32 weeks' gestation, inducing strong gastric and pyloric bulb contractions and resulting in an enlarged pylorus (pyloric hypertrophy). Symptoms of IHPS range from projectile vomiting and dehydration to weight loss and electrolyte abnormalities, explains Wayne A. Ray, Ph.D., of the Center for Education and Research in Therapeutics (CERT) at Vanderbilt University.

In the study, which was supported in part by the Agency for Healthcare Research and Quality (HS10384), Dr. Ray and his colleagues analyzed births among women enrolled in Tennessee's Medicaid/TennCare from 1985 to 1997 (260,799 mother/infant pairs) and prenatal prescriptions for erythromycin, nonerythromycin macrolides, and other antibiotics from pharmacy files linked with birth certificate files.

A previous study by the same researchers (in the October 2002 issue of Research Activities) found an increased risk of IHPS among infants who received erythromycin before 2 weeks of age. The current study found no association with prenatal erythromycin prescriptions and IHPS either after 32 weeks' gestation or at any time during pregnancy. There was an association between maternal prescriptions for nonerythromycin macrolides and IHPS, but the evidence was limited by the small number of affected children. Also, more mothers taking these antibiotics were black and urban and had sexually transmitted diseases which, along with other unmeasured factors, may have affected development of IHPS, note the researchers.

More details are in "Prenatal prescription of macrolide antibiotics and infantile hypertrophic pyloric stenosis," by William O. Cooper, M.D., M.P.H., Dr. Ray, and Marie R. Griffin, M.D., M.P.H., in the July 2002 Obstetrics & Gynecology 100(1), pp. 101-106.

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