Objective: To examine associations of vaginal Ureaplasma urealyticum (UU) and bacterial vaginosis (BV) with preterm delivery (PTD), small for gestational age (SGA), and low birth weight (LBW).
Material and methods: A population-based, prospective cohort study of 2,927 pregnancies. After exclusion of multiples and antibiotic use sample size was 2,662. BV (Amsel's criteria) and UU (culture) were assessed in week 17. Gestational age was determined by last menstrual period, confirmed by ultrasound measurement in 97.5%. SGA infants were calculated from intrauterine fetal growth measurements.
Results: There was no increased risk for spontaneous PTD among women with BV only (crude odds ratio 1.0, 95% CI 0.4-2.7), among women with UU only (1.3, 0.8-2.0), nor among women with UU + BV (0.9, 0.4-2.3) compared to women without UU and BV. However, there was a threefold increased risk of a LBW birth in women with UU + BV (3.1, 1.8-5.4), a twofold risk of a LBW birth among women with UU only (1.9, 1.3-2.9), but no increased risk among women with BV only (0.8, 0.3-2.2). Similarly, women with UU + BV had over a twofold increased risk of an SGA birth (2.3, 1.3-4.0), women with UU only had a 70% increase (1.7, 1.1-2.5), whereas a nonsignificant increase was found in women with BV only (1.3, 0.6-2.9). Adjustment by established confounders (smoking, previous PTD, previous LBW, and Escherichia coli) did not affect risk estimates.
Conclusion: This analysis suggests that UU is independently associated with fetal growth and LBW and that BV with UU may enhance the risk of these outcomes.