Erythromycin use during pregnancy in relation to pyloric stenosis

Objective: Newborn infants treated with erythromycin may be at risk for developing pyloric stenosis. Because erythromycin is known to cross the placenta and is a recommended treatment for chlamydia and other infections in pregnancy, we explored whether erythromycin taken during pregnancy might similarly lead to an increase in risk of pyloric stenosis. Study Design: We used data collected between 1976 and 1998 as part of an ongoing case-control surveillance program. Cases were 1044 infants with a diagnosis of pyloric stenosis. Two control groups were used: 1704 nonmalformed infants and 15,356 infants with a wide range of other malformations. Odds ratios and 95% CIs were calculated by using data from each control group. Results: All odds ratio estimates are close to 1.0, all CIs include 1, and all upper 95% confidence bounds are less than 2.0. Conclusion: We found no evidence of an increased risk of pyloric stenosis among infants born to mothers exposed to erythromycin during pregnancy. (Am J Obstet Gynecol 2002;186:288-90.)