Study of ampicillin levels in maternal serum, umbilical cord serum and amniotic fluid following administration of pivampicillin.

Premature rupture of the membrane is often followed by intrauterine infections. Antibiotic prophylaxis is recommended, but the effect has been debatable. Thirty pregnant women received pivampicillin 350 mg 4 times daily. The ampicillin levels in amniotic fluid and in the serum of the fetus and of the mother were determined and related to pivampicillin dose and time after administration. In the amniotic fluid the average concentration was 3.4 micrograms/ml, which is considered therapeutic. In maternal and fetal serum the ampicillin concentrations were low and took an almost parallel course. To obtain the same ratio between ampicillin serum levels and MIC (minimum inhibitory concentration) in the pregnant as in the non-pregnant subject, a double dosage should be used.