Bacterial Vaginosis in Pregnancy

Bacterial vaginosis (BV) in pregnancy is a polymicrobial disturbance of the vaginal flora in which lactobacilli are replaced by Gardnerella vaginalis, Prevotella, Mobiluncus, Atopobium and anaerobes. It affects 10 to 30 percent of pregnant women in Africa.

• Risk factors: previous BV, multiple or new partners, douching, smoking, black ancestry, HIV, low socioeconomic status.
• Associated with preterm birth, late miscarriage and chorioamnionitis.

Thin, grey white homogeneous discharge with fishy odour, worse after sex or menses; little itching or soreness; about half of women are asymptomatic.

• Diagnosis by clinical criteria: thin discharge, vaginal pH over 4.5, positive whiff test and clue cells (three of four).
• Differential diagnosis: trichomoniasis, vulvovaginal candidiasis, cervicitis (gonorrhoea, chlamydia), physiological discharge, retained foreign body, cervical insufficiency with leakage of fluid (premature rupture of membranes), cytolytic vaginosis, desquamative inflammatory vaginitis.
• Complications: preterm labour, preterm prelabour rupture of membranes, late miscarriage, low birth weight, chorioamnionitis, postpartum endometritis, post caesarean wound infection, increased acquisition of HIV and other STIs.

Clinical criteria or Gram stain.

• Vaginal swab: pH strip, whiff test with 10 percent potassium hydroxide, microscopy for clue cells, Gram stain scoring (score of 7 to 10 is diagnostic).
• Test for trichomonas, candida, chlamydia, gonorrhoea; HIV and syphilis tests; urine culture for asymptomatic bacteriuria.
• Screen and treat asymptomatic women with a previous preterm birth.

Treat symptomatic women at any stage; treat asymptomatic high risk women early.

• Supportive: avoid douching and perfumed products, cotton underwear, condoms, avoid sex until treated, counselling on symptoms of preterm labour.
• Pharmacological: metronidazole 400 mg (or 500 mg) orally twice daily for 7 days, acceptable in all trimesters; or clindamycin 300 mg orally twice daily for 7 days; or metronidazole gel 0.75 percent 5 g intravaginally once daily for 5 days. Clindamycin vaginal cream is avoided in late pregnancy. Recurrence: repeat the course, and give suppressive metronidazole gel 0.75 percent twice weekly for 4 to 6 months. Asymptomatic women with previous preterm birth: treat before 20 weeks.
• Procedures: none; cervical cerclage is not a BV treatment.
• Special groups: HIV, treat and screen for other STIs; breastfeeding, metronidazole 400 mg twice daily is acceptable; women with premature rupture of membranes, culture and treat; partners, treatment is not routinely needed.
• Red flags: preterm contractions, rupture of membranes, fever, abdominal pain, offensive purulent discharge, bleeding.
• Follow-up: test of cure at 3 to 4 weeks if symptoms persist or high risk; rescreen at 28 weeks; monitor cervical length in women with preterm history.