Which drug should NOT be given during pregnancy according to the provided information?

Tetracyclines should not be given during pregnancy because they can affect fetal development. This class of antibiotics is known to cross the placenta and can cause discoloration of the teeth in the developing fetus as well as interfere with bone growth. Due to these significant potential risks, their use is contraindicated during pregnancy, particularly during the second and third trimesters when fetal bone and teeth development is most active.

In contrast, cephalosporins, penicillins, and azithromycin are generally considered safer options during pregnancy. These antibiotics have been studied more extensively with regard to their effects on fetal development, and their use can be warranted when the benefits outweigh potential risks. The emphasis during pregnancy is always on safeguarding the health of both the mother and the developing fetus, which is why tetracyclines are specifically restricted.