Metronidazole is used to treat a variety of infections. It belongs to a class of antibiotics known as nitroimidazoles. It works by stopping the growth of bacteria and protozoa. This antibiotic only treats bacterial and protozoal infections. During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor. Studies have not shown any adverse effects in rats, however it is not given in first trimester of pregnancy. In third trimester it can be given, but better to take under medical supervision. Regards Dr Santosh