Combination of vaginal pH with vaginal sialidase and prolidase activities for prediction of low birth weight and preterm birth

Objective The purpose of this study was to assess if easy to measure vaginal fluid biomarkers are predictive for low birth weight (LBW, <2500 g), very LBW (VLBW, <1500 g), spontaneous preterm at <37 weeksʹ gestation, and total preterm deliveries (at <37, <35, <32 weeksʹ gestation). Study design Low and high cutoffs for vaginal fluid pH, sialidase, and prolidase activities were examined in a nested case-control study of 579 Danish women (from a study population of 2846 women) with samples collected at mean 17 weeksʹ gestation. One hundred sixteen LBW (17 VLBW), 117 preterm deliveries (85 spontaneous), and 418 normal term deliveries were analyzed. Results Vaginal pH ≥4.7 or pH ≥5 by itself was not associated with LBW or prematurity. Conversely, combination of pH ≥5 and high sialidase activity demonstrated OR 17 (CI 1.8-150) for LBW; OR 31 (CI 1.8-516) for VLBW; along with OR 18 (CI 1.6-204) for preterm at <35 weeksʹ; and OR 31 (CI 1.9-542) for preterm at <32 weeksʹ gestation. The combination of pH ≥5 and high prolidase activity demonstrated OR 13 (CI 1.3-122) for LBW; OR 33 (CI 2.0-553) for VLBW, as well as OR 9.2 (CI 0.6-150) for preterm at <35 weeksʹ; and OR 35 (CI 2.0-586) for preterm at <32 weeksʹ gestation. In this population, no woman having high sialidase and high prolidase activity had a term birth, or a baby weighting ≥2500 g at birth. Conclusion In this Danish population, mid-gestation findings of vaginal fluid elevated pH with sialidase and/or prolidase were associated with LBW, VLBW, and early preterm at <35 or <32 weeksʹ gestation.