Metronidazole taken in the fourth week of pregnancy has effects that may cause abnormal fetal development. Metronidazole passes through the human placenta, and rodent studies have shown no evidence of teratogenicity or intrauterine growth retardation, even when higher than clinically indicated doses are used. There are no adequate and validated controlled studies of metronidazole in pregnant women, and metronidazole is safe when used for short-term treatment, with some studies showing an increased risk of cleft lip with or without cleft palate in infants exposed to metronidazole in utero. Early pregnancy is an important stage of fetal development, and this is the time to avoid any medications that may have an adverse effect on pregnancy. If medication is needed during pregnancy, it is necessary to follow the doctor’s instructions strictly and avoid using medication at your own discretion.