Is bacterial vaginosis a stronger risk factor for preterm birth when it is diagnosed earlier in gestation?
OBJECTIVE
It is stated commonly that the earlier in pregnancy bacterial vaginosis is diagnosed, the greater is the increase in risk of preterm birth compared with women without bacterial vaginosis. However, this contention is based on small numbers of women.


METHODS
In this analysis of 12,937 women who were screened for bacterial vaginosis as part of a previously conducted clinical trial, the odds ratio of preterm birth (<7 weeks of gestation) for asymptomatic bacterial vaginosis-positive versus bacterial vaginosis-negative women was evaluated among women who were screened from 8 to 22 weeks of gestation.


RESULTS
The odds ratio of preterm birth among bacterial vaginosis-positive versus bacterial vaginosis-negative women ranged from 1.1 to 1.6 and did not vary significantly according to the gestational age at which bacterial vaginosis was screened. The odds ratio for preterm birth did not vary significantly by gestational age at diagnosis when bacterial vaginosis was subdivided into Gram stain score 7 to 8 or 9 to 10.


CONCLUSIONS
Although bacterial vaginosis was associated with an increased risk of preterm birth, the gestational age at which bacterial vaginosis was screened for and diagnosed did not influence the increase.
Klebanoff
Mark A
MA
National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA. mk90h@nih.gov
Hillier
Sharon L
SL
Nugent
Robert P
RP
MacPherson
Cora A
CA
Hauth
John C
JC
Carey
J Christopher
JC
Harper
Margaret
M
Wapner
Ronald J
RJ
Trout
Wayne
W
Moawad
Atef
A
Leveno
Kenneth J
KJ
Miodovnik
Menachem
M
Sibai
Baha M
BM
Vandorsten
J Peter
JP
Dombrowski
Mitchell P
MP
O'Sullivan
Mary J
MJ
Varner
Michael
M
Langer
Oded
O
D005260:Female; D005865:Gestational Age; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D016017:Odds Ratio; D011247:Pregnancy; D047928:Premature Birth / Q000209:etiology*; D012307:Risk Factors; D016585:Vaginosis, Bacterial / Q000150:complications* / Q000175:diagnosis