The relationships among umbilical artery velocimetry, fetal biophysical profile, and placental inflammation in 44 consecutive patients with preterm premature rupture of the membranes were determined. All patients were followed up with daily fetal biophysical profiles and systolic/diastolic ratios. After delivery, placental pathologic examination for histologic evidence of infection (umbilical vasculitis) was performed in all cases according to a standard protocol. The longitudinal trends of fetal biophysical profile scores and systolic/diastolic ratios were analyzed for patients with and without umbilical vasculitis. Analysis of the longitudinal trend during the period of 2 to 7 days before delivery showed that there were no differences of biophysical scores of systolic/diastolic ratios in either group. However, in the last examination, within 24 hours of delivery, patients with umbilical vasculitis had higher systolic/diastolic ratios and lower biophysical profile scores as compared with previous examinations. In addition, the biophysical profile score of the last examination 24 hours before delivery in patients with umbilical vasculitis was found to be significantly lower as compared with patients without umbilical vasculitis (mean +/- SD, 6.6 +/- 2.3 versus 8.2 +/- 2.4, respectively). These data suggest that subclinical stages of infection are associated with biophysical alterations of the fetoplacental unit (i.e., simultaneous decrease in fetal biophysical activities and increase in systolic/diastolic ratios). Daily umbilical artery systolic/diastolic ratios, in conjunction with biophysical profiles, may be useful to follow up patients with preterm premature rupture of the membranes.