Lower genital tract swabs in the prediction of intrauterine infection in preterm prelabour rupture of the membranes

Objective To examine the genital tract flora in women with preterm prelabour rupture of the membranes and to determine the relationship of these microorganisms to those found in fetal blood and amniotic fluid. Design Prospective study of 97 patients with preterm prelabour rupture of the membranes. Setting Maternal-fetal medicine centre. Methods High vaginal and endocervical swabs were taken for routine culture of aerobic and anaerobic bacteria and Ureaplasma urealyticum and Mycoplasma hominis. Cordocentesis and amniocentesis were performed and fetal blood and amniotic fluid were cultured for aerobic and anaerobic bacteria. Amniotic fluid was also cultured for Mycoplasma spp. The sensitivities and specificities of genital tract colonisation in the prediction of fetal blood and amniotic fluid infection were calculated. Results Positive genital tract cultures for aerobic and anaerobic organisms predicted 40% of positive fetal blood and 53% of positive amniotic fluid cultures with false positive rates of 24% and 25%. respectively. The sensitivity and false positive rates for genital tract colonisation with Mycoplasma spp in the prediction of amniotic fluid infection with these organisms were 85% and 35%, respectively. Conclusions In preterm prelabour rupture of the membranes lower genital tract cultures provide poor prediction of intrauterine infection.