To evaluate the efficacy of imipenem/cilastatin sodium (IPM/CS) in the field of obstetrics and gynecology, fundamental (measurement of IPM/CS concentrations in mothers' milk) and clinical studies were performed. Concentrations of IPM/CS in mothers' milk were measured every 1 hour up to 6 hours after a 30-minute drip infusion of 500 mg/500 mg of IPM/CS. IPM/CS was distributed similarly to other cephalosporins. In the clinical study, a 500 mg/500 mg dose of IPM/CS was administered to 5 patients with puerperal intrauterine infections and to 3 patients with urinary tract infections by a 30-minute drip infusion b.i.d. or t.i.d. Good responses were observed in all 8 patients, though the infections were mild or moderate. From these results, IPM/CS appeared to be a useful drug for the treatment of perinatal infections.