Isolated reports note that newborns whose mothers received tricyclics just before delivery may have tachycardia, respiratory distress, and urinary retention. Cardiovascular abnormalities, including Ebstein's anomaly, were most common. In children exposed to tetracyclines in utero, teeth may be permanently yellow and less resistant to caries, enamel hypoplasia may occur, and bone growth may be retarded. Because several safe alternatives are available, tetracyclines should be avoided during pregnancy. Streptomycin, gentamicin, kanamycin, and other ototoxic drugs should be avoided in pregnancy because they cross the placenta and may damage the fetal labyrinth.
Penicillins appear to be safe.
If the sulfonamides are given before about the 34th wk, the placenta efficiently excretes the bilirubin, minimizing fetal risk. When sulfonamides are given near delivery, the newborn may develop jaundice and, if untreated, kernicterus. An exception is sulfasalazine, whose active fetal metabolite, sulfapyridine, has weak bilirubin-displacing activity, posing minimal risk to the fetus. Cephalosporins are often considered during pregnancy, but because studies in humans cannot rule out the possibility of harm, cephalosporins should be used during pregnancy only if clearly needed. The use of quinolone antibiotics during pregnancy has recently been questioned because of reports that ciprofloxacin and norfloxacin have a high affinity for bone and cartilage, potentially causing arthralgia in exposed children.