Hello,
Welcome to the ehealthforum and I am glad to help you. No reports linking the use of erythromycin with congenital defects have been found. The drug has also not been found to be teratogenic in animals.
Erythromycin does cross the placenta but in really low concentrations. Overall, the data does not support an association between the drug and congenital malformations.
Hence, erythromycin can be taken during the pregnancy. I sincerely hope that helps. Take care.