Bacterial Vaginosis in Pregnancy: A Comprehensive Guide for Moms-to-Be

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Bacterial Vaginosis in Pregnancy: A Comprehensive Guide for Moms-to-Be

Vaginal infection is known as Bacterial vaginosis (BV), which affects many women of reproductive age. Vaginal imbalance of the microbial ecosystem is its cause. Although it is often asymptomatic, the most common presenting symptoms of BV are odor and discharge.

It is particularly concerning when it is identified during pregnancy. Although BV is associated with pregnancy complications, there is no clarity on the best methodology for screening, diagnosis & management.

This article explores the causes, risks, and management of bacterial vaginosis in pregnancy. We will cover testing options, the safety of antibiotics, consequences left untreated, and how to lower recurrence. Read on for insights into protecting both maternal and infant health in the setting of this delicate bacterial imbalance.

Causes of Bacterial Vaginosis During Pregnancy

Bacterial Vaginosis in pregnancy develops in the event of excessive growth of anaerobic bacteria in the vagina and the decrease of lactobacilli bacteria that are healthy. However, researchers continue to unravel the specific cause of such imbalance being triggered.

Potential causes and contributing factors include:

  • Hormone fluctuations that change vaginal acidity
  • Introduction of foreign bacteria through practices like douching
  • Use of antibiotics that kill off normal vaginal bacteria
  • Semen exposure that alters microbial composition
  • Elevated vaginal pH above 4.5
  • Genetic predisposition and ethnicity, especially African descent
  • Prior damage to the vaginal epithelium
  • Other underlying illnesses like diabetes or HIV

During pregnancy, shifts in estrogen levels in particular may increase susceptibility to bacterial imbalance. One study found BV prevalence increased from 13% in week 10 up to 22% by week 20 of gestation.

Risks of Bacterial Vaginosis During Pregnancy

For pregnant patients, BV carries risks including:

  • Preterm birth: Studies consistently associate BV with a 1.5 to 2-fold higher chance of preterm delivery. The infection provokes an inflammatory response.
  • Low birth weight: BV ties to double the risk of giving birth to an infant with a low birth weight below 2500g.
  • Amniotic fluid infection: Bacteria ascending into fluids and membranes can cause chorioamnionitis, sepsis, etc.
  • Postpartum endometritis: Inflammation of the uterine lining after delivery may occur.
  • Post-abortal sepsis: BV increases infectious risks if pregnancy is terminated.
  • Miscarriage: Potential link to first-trimester pregnancy loss, perhaps due to placental inflammation.
  • Post-cesarean wound complications: Increased risk of wound disruption or abscess after C-section delivery.

Fortunately, the majority of pregnancies affected by BV will still result in healthy, full-term deliveries. However, complications are elevated enough to warrant identification and treatment.

Testing for Bacterial Vaginosis in Pregnancy

Standard diagnostic options for bacterial vaginosis include:

  • Amsel’s criteria – Physician evaluates discharge, clue cells under the microscope, pH greater than 4.5, and positive “whiff” test. The presence of 3 criteria indicates BV.
  • Gram stain – Nugent scoring of the slide with vaginal swab determines bacterial morphologies present. A score above 6 confirms BV.
  • DNA probe – Identifies the presence of sialidase enzyme produced by BV-associated bacteria.
  • OSOM BV Blue test – Mixes vaginal fluid with a reagent for colorimetric detection of increased vaginal pH and sialidase. Blue indicates BV positive.
  • Affirm VPIII – Microbial culture identifies pathogenic bacteria associated with BV and yields gram stain results.

BV testing can be performed at the first prenatal visit, during mid-pregnancy, and whenever symptoms like odor or discharge arise. Testing around weeks 16-20 helps detect emerging bacterial imbalance.

Treating Bacterial Vaginosis in Pregnancy

Centerstone guidelines endorse antibiotic treatment with either oral metronidazole or vaginal clindamycin creams to alleviate Bacterial vaginosis in pregnancy. Potential antibiotic regimens include:

  • Oral metronidazole 500 mg twice daily for 7 days
  • Metronidazole gel 0.75%, one applicator (5 g) intravaginally once a day for 5 days
  • Clindamycin cream 2%, one applicator (5 g) intravaginally at bedtime for 7 days

Oral and vaginally applied antibiotics have comparable efficacy and safety for treating Bacterial vaginosis in pregnancy.

Some studies have explored using probiotics after antibiotic therapy to lengthen the time to Bacterial vaginosis in pregnancy recurrence. However current evidence on specific strains and dosing is limited. Probiotic use should be discussed with the obstetrician.

Weighing the Risks and Benefits of Antibiotic Use

While antibiotics are the standard therapy for Bacterial vaginosis in pregnancy, there are some concerns with their use in pregnancy:

Potential risks include:

  • Digestive side effects like nausea or diarrhea from oral metronidazole
  • Allergic reaction in penicillin-allergic patients for clindamycin
  • Risk of masking a concurrent sexually transmitted infection
  • Fetal exposure through placental passage of medication

However, topical vaginal treatment results in very low systemic absorption. Studies find no evidence of teratogenicity, mutagenicity, or increased adverse outcomes in newborns with either oral or vaginal antibiotic use.

Experts conclude the benefits of antibiotic therapy appear to clearly outweigh the low risks during pregnancy. Leaving Bacterial vaginosis in pregnancy untreated poses more danger to the fetus.

Can Bacterial Vaginosis Be Prevented During Pregnancy?

Preventing initial Bacterial vaginosis in pregnancy recurrence requires focusing on modifiable risk factors:

  • Avoid douching, irritating soaps, glitter bath bombs, etc. as these disrupt the vaginal environment.
  • Use condoms correctly to lower the transmission of bacteria from semen exposure.
  • Stop smoking and substance use, as these worsen bacterial imbalance.
  • Manage diabetes through diet, exercise, and medication to control blood sugars.
  • Request STI testing if new or multiple partners to rule out co-occurring STIs like trich or chlamydia.
  • Incorporate daily probiotic supplements containing lactobacilli strains such as L. crispatus, L. acidophilus, L. gasseri, and L. jensenii into your routine.

Probiotic vaginal suppositories may also help prevent initial cases of bacterial vaginosis. Maintaining a balanced vaginal pH and microbiome optimizes reproductive health during pregnancy.

Frequently Asked Questions

Here are some common questions about BV in expecting mothers:

Q: Should male sex partners be treated for BV exposure?
Answer: Current guidelines do not recommend empirically treating male partners if they are asymptomatic. Ensure partners get STI testing.

Q: How soon after finishing antibiotics for BV is it safe to have sex?

Answer: It is recommended to abstain from intercourse until BV symptoms resolve and the antibiotic course finishes. This helps prevent reinfection or recurrence.

Q: Will my baby get bacterial vaginosis from me during delivery?

Answer: Infants may have brief colonization of vaginal bacteria during birth. But BV itself does not infect newborns long-term if properly treated.

Q: Is bacterial vaginosis common during the first trimester?

Answer: BV rates are relatively low in very early pregnancy but tend to increase during the mid-second trimester around weeks 16-20.

Q: Can untreated BV in pregnancy harm the baby long-term?

Answer: Research on long-term impacts is limited. Prompt antibiotic treatment helps avoid lasting issues.

By identifying and addressing Bacterial vaginosis in pregnancy through antibiotic therapy, pregnant women can greatly reduce risks of adverse pregnancy outcomes.


Dysbiosis of the vaginal flora causes bacterial vaginosis in up to thirty percent of pregnant women. Untreated BV results in pre-term births, low birth weight, and post-partum infection. Screening for BV should occur in early and mid-pregnancy. Oral or vaginal antibiotic treatment alleviates bacterial overgrowth and inflammation while posing low fetal risks. Preventing BV recurrence involves moderating risk factors like douching, smoking, and vaginal pH changes. Prompt antibiotic treatment protects both maternal and infant well-being.


Bacterial vaginosis in pregnancy requires clinical attention but not alarm. Following professional guidelines for accurate diagnosis, antibiotic therapy, and risk factor reduction allows expecting mothers with BV to continue towards healthy pregnancies. Work closely with your obstetrician for proper screening and treatment if signs of BV arise. Stay vigilant for symptoms like odor or discharge that could signal infection. With appropriate management guided by compassionate care, even vulnerable pregnancies complicated by bacterial vaginosis can progress safely toward joyful, thriving newborn outcomes.


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