Spectinomycin Spectinomycin is related to the aminoglycoside antibiotics. The drug is FDA category B, and is not known to cause fetal harm. It can be an effective alternative for the treatment of gonorrhea infections pregnant women who are allergic to penicillin and cephalosporin drugs. Metronidazole is used to treat trichomonas vaginalis infections, which can be the cause of significant vaginal irritation. It has not been demonstrated to be harmful to human fetuses.
Metronidazole does cause cancer in rodent studies.
However, this effect has not been demonstrated in other animal models. The drug should not be prescribed during the first trimester of pregnancy, and should only be used if clearly needed. If resistance to INH seems likely, ethambutol should also be added. Isoniazid has not been shown to cause birth defects or other fetal harm in humans. Neither has its use been demonstrated to cause birth defects in animal studies, although the drug may cause embryo death in rats and rabbits and can cause lung cancer in specific strains of mice.