Bacterial vaginosis in pregnancy

By trimester

Weeks 1–13

1st trimester

First-trimester BV carries the strongest association in the literature, including a three- to fivefold higher chance of early pregnancy loss. That makes new discharge or odor now worth mentioning rather than filing under normal pregnancy changes.

Weeks 14–27

2nd trimester

Discharge naturally increases through the second trimester, which blurs the signal. A change in smell, color, or consistency is the part that separates ordinary discharge from something worth a swab.

Weeks 28–birth

3rd trimester

BV has been associated with premature rupture of membranes and preterm delivery, so late-pregnancy symptoms get taken seriously. Fluid leaking is always a separate and more urgent call.

What does the evidence show for bacterial vaginosis?

• BV is a shift in the vaginal microbiome, with fewer hydrogen-peroxide-producing lactobacilli and an overgrowth of anaerobic bacteria, and it involves multiple organisms rather than a single one. 1
• Many people with BV have no symptoms at all, the typical presentation is a thin gray or white discharge with a distinct odor, and roughly 30 percent of cases resolve on their own. 1
• In pregnancy, BV is associated with a twofold higher risk of preterm delivery and a three- to fivefold higher risk of spontaneous abortion when found in the first trimester, along with chorioamnionitis, premature rupture of membranes, and postpartum endometritis. 1
• In a cohort of 237 pregnancies, BV was present in 10.1 percent, and those pregnancies had more delivery before 34 weeks (22.7 versus 6.2 percent) and a lower median birth weight (2,450 versus 2,950 grams). 2
• Bacterial vaginosis appears on the federal list of infections that can affect a pregnancy, alongside conditions like CMV, listeria, group B strep, and toxoplasmosis. 3

When should I call my provider about bacterial vaginosis?

Bacterial vaginosis is described as thin gray or white discharge with a fish-like odor, so fever plus pelvic pain is a different picture and raises the question of pelvic inflammatory disease instead. Get seen the same day for discharge that arrives with pelvic or lower abdominal pain, fever, or painful urination, and for itching or a thick discharge that suggests something other than BV. Because BV in pregnancy carries an association with preterm delivery, premature rupture of membranes, and chorioamnionitis, fluid that leaks or gushes, vaginal bleeding, or regular tightening before 37 weeks belongs in an urgent call rather than a next-visit note. When in doubt, call your obstetric team the same day. Early input almost always beats waiting, and the on-call line exists exactly for this.