Which antibiotic class is contraindicated in pregnancy due to potential fetal harm?

Tetracyclines are contraindicated in pregnancy because they can cross the placenta and affect fetal development. This class of antibiotics is known to cause several adverse effects on the fetus, including impaired bone growth and discoloration of teeth. Tetracyclines inhibit the formation of bones and teeth by chelating with calcium, magnesium, and iron, leading to potential long-term developmental issues for the child.

The other antibiotic classes listed have different safety profiles. For example, beta-lactams, which include penicillins and cephalosporins, are generally considered safe during pregnancy and are often used for treating infections in pregnant patients. Macrolides have also been deemed relatively safe, although there may be some caveats depending on the specific agent and timing of exposure. Glycopeptides, like vancomycin, can be used cautiously in pregnancy and are sometimes necessary for serious infections, though they are not first-line treatments.

However, tetracyclines stand out due to their well-documented risks to fetal development, making them a clear choice as contraindicated during pregnancy.