Vaginal pH versus cervical length in the mid-trimester as screening predictors of preterm labor in a low-risk population.
OBJECTIVE
To assess the accuracy of a sign of bacterial vaginosis and a sign of cervical insufficiency in predicting preterm labor (PTL, occurring in the 37th week or earlier) and early PTL (occurring in the 34th week or earlier) in a low-risk cohort of 316 pregnant women.


METHODS
Vaginal pH was assessed using test gloves and cervical length (CL) was measured by transvaginal ultrasound. A pH value less than 5.0 (the 95th-percentile threshold) and a CL greater than 26 mm (the 5th-percentile threshold) were considered normal.


RESULTS
There were 14 participants (4.4%) with an elevated vaginal pH and 15 (4.7%) with a shortened CL. The incidence of PTL (<37 weeks) was 7.2%, while incidence of early PTL (≤34 weeks) was 2.5%. A shortened CL was significantly correlated with PTL (likelihood ratio [LR] weighted by prevalence; 2.7; 95% CI, 1.1-6.7) but not with early PTL (LR, 0.8; 95% CI, 0.4-1.8). An elevated vaginal pH was a better predictor of PTL (LR, 3.7; 95% CI, 1.3-10.4) and early PTL (LR, 1.7; 95% CI, 1.1-3.1).


CONCLUSIONS
An elevated vaginal pH was a better predictor of early PTL than a shortened CL in this cohort of pregnant women at low risk.
Matijevic
Ratko
R
University Department of Obstetrics and Gynecology, School of Medicine, Sveti Duh Hospital, Zagreb, Croatia.
Grgic
Ozren
O
Knezevic
Mario
M
D000328:Adult; D054791:Cervical Length Measurement / Q000379:methods* / Q000706:statistics & numerical data; D002584:Cervix Uteri / Q000000981:diagnostic imaging; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007752:Obstetric Labor, Premature / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D015995:Prevalence; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal / Q000379:methods; D014621:Vagina / Q000000981:diagnostic imaging* / Q000382:microbiology*; D016585:Vaginosis, Bacterial / Q000150:complications* / Q000453:epidemiology