Is oligohydramnios a risk factor for infection in term premature rupture of membranes?

Our objective was to determine if a reduced volume of amniotic fluid is a risk factor for microbial invasion of the amniotic cavity in women with rupture of membranes at term. Transabdominal amniocentesis under ultrasound guidance was used to evaluate the microbiological state of the amniotic cavity in 53 patients with term premature rupture of membranes before vaginal examination. Amniotic fluid index was measured prior to the procedure in all cases. The prevalence of microbial invasion of the amniotic cavity was 32.1% (17/53). Women with microbial invasion of the amniotic cavity had a significantly lower median amniotic fluid index than did women without evidence of infection (median 4.4 cm, range 1.0-8.1 vs. median 7.8 cm, range 1.3-14.4, respectively; p < 0.001). An amniotic fluid index of < 5 cm had a sensitivity of 71% (12/17) a specificity of 89% (32/36), a positive predictive value of 75% (12/16) and a negative predictive value of 87% (32/37) in the prediction of microbial invasion of the amniotic cavity. Among women who delivered vaginally, those with an amniotic fluid index of < 5 cm had a higher rate of endometritis than those with an amniotic fluid index of >or= 5 cm (19% (3/16) vs. 0% (0/26), respectively; p < 0.05). We conclude that women with term premature rupture of membranes and an amniotic fluid index of < 5 cm are at an increased risk for microbial invasion of the amniotic cavity and puerperal infection after a vaginal delivery.