In most published studies, erythromycin therapy during pregnancy was not associated with an increase in the risk of birth defects.
There is limited evidence suggesting a small increase in the risk of congenital heart disease and pyloric stenosis, however, data is conflicting and this was not confirmed in other samples.
Decreased neonatal morbidity and mortality and longer duration of gestation have been observed in clinical trials of erythromycin treatment of pregnant women with premature rupture of the membranes.
Erythromycin estolate specifically is avoided in pregnancy due to potential maternal hepatotoxicity.
Because of the low levels of erythromycin in breastmilk and use in infants in higher doses, it would not be expected to cause significant adverse effects in breastfed infants.
A case report and cohort study indicate that the risk of infantile hypertrophic pyloric stenosis might be increased by maternal use of erythromycin during the first two weeks of breastfeeding, but this has not been confirmed and data is conflicting.
Monitor the infant for gastrointestinal intolerance.