Bacterial vaginosis (BV) is one of the most common genital tract infections in pregnancy, more so in the African population. It is a syndrome marked by an increased vaginal pH, milky creamy discharge and amine or fishy odor. It is characterized by a shift in the vaginal flora from the dominant lactobacillus species to a mixed vaginal flora. The number of lactobacilli morphotypes is reduced and the number of anaerobic bacterial morphotypes like Gardnerella vaginalis, Prevotella, Mobilincus species, and Mycoplasma hominis is increased 1.
The magnitude and determinants of BV have been observed to be varying from one place to another due to the differences in geographical, socio-economical and clinical characteristics of the study populations. The prevalence of BV ranges from 4 to 64%, depending on the racial, geographic and clinical characteristics of the study population. Several factors have been associated with the causation of BV, these include younger age, black race, lower socioeconomic status, smoking, vaginal douching, early sexual activity, multiple sexual partners, history of current or Sexually Transmitted Disease (STI) and Human Immunodeficiency Virus infection (HIV). About 50% of the women with BV are asymptomatic. If symptomatic, commonly present with a malodorous discharge and usually there are no clinical signs of infection in the vaginal mucosa 1.
Several clinical and microscopic scoring systems for the diagnosis of BV have been validated. The most commonly used are the Amsel’s criteria and the gold standard laboratory based Nugent Gram staining evaluation. Slides of vaginal smears are Gram stained and the bacterial morphotypes are quantified and scored as follows: Large Gram-positive rods (Lactobacillus scored as 0 to 4), small Gram-variable rods (Gardnerella vaginalis scored as 0 to 4) and curved Gram-variable rods (Mobiluncus species scored as 0 to 2). Bacterial vaginosis is put on a 10-point scale where:0-3 is regarded as normal (predominantly Lactobacillus), 4-6 as intermediate (mixed flora) and 7-10 positive for BV (no Lactobacillus) 2.
Bacterial vaginosis is associated with adverse maternal and perinatal outcomes such intrauterine infections, chorioamnionitis, postpartum endometritis, spontaneous abortion, preterm labor (PTL), premature rupture of membrane (PROM), low birth weight babies, neonatal sepsis and death 3-5. Intrauterine infections may occur early in pregnancy or even before pregnancy and remain asymptomatic and undetected for months until PTL or PROM occurs. Preterm labor and delivery are among the most challenging obstetric complications encountered.
Although several studies have been done Tanzania showing prevalence in different sub groups. No recent study has been conducted among pregnant women attending ANC to determine the prevalence and predictors of BV. Given the probable association of BV and poor pregnancy outcome, it calls for need of studying and understanding the situation in the local settings. Determining the predictors of BV could be the best way of knowing women at high risk of developing the disease, screening them early and managing them appropriately if diagnosed to have the infection. Therefore this could have a substantial impact in preventing adverse pregnancy and neonatal outcomes associated with BV which in turn decreases the cost factors, morbidity and mortality rates for both mother and neonate. This study was therefore designed to find out the prevalence of BV and its predictors among pregnant women attending antenatal clinic at Muhimbili National Hospital (MNH).
The prevalence of BV in this study was noted to be high which can be explained by the fact that certain behavioral factors such as douching are practiced by majority of the women in Dar es Salaam 6. Higher prevalence has also been reported in several sub Saharan countries including Nigeria, Botswana, Kenya, and Zimbabwe 7-9. In contrast lower prevalence was reported in Portugal, Burkina Faso, and India 10–12. This vast difference in prevalence across the globe is presumably due to environmental, behavioral, socioeconomic status and stressor differences in the geographical variation.
The highest prevalence of BV occurred among women in their 20s. Similar findings were reported in studies done in Nigeria whereby women aged 21-30 were predominantly diagnosed to have BV as compared to other age groups 7,13. In comparison a French population based study reported maternal age of less than 20 years to be significantly associated with BV as compared to older women 14. Others have reported highest prevalence of BV among women aged more than 30 years 15. The common finding in all these studies is that the age groups with the highest prevalence of BV are the most sexually active age group with the highest risk of pregnancies and STIs 15. More than 50% of the participants in this study were in their 20s hence this could account for the high prevalence noted among this age group. Considering the urban setting of the study, women below 20 years are less likely to get pregnant due to more awareness, accessibility and availability of contraceptives.
It was noted that women who had a primary education and less were more likely to get BV as compared to women who had a secondary education and above. In a randomized controlled trial done in France it was seen that women with a primary education were two fold more likely to get BV 14. A study done in Nigeria also noted similar findings whereby lack of western education was associated with increased risk of BV 16. This could possibly explained by the fact that women with low education levels may not be knowledgeable about certain harmful practices such as vaginal douching and may also delay in seeking appropriate treatment for conditions such as STI.
Women who douched during pregnancy were significantly more likely to get BV as compared to women who did not douche. This finding is due to the fact that the majority of the women in this study douched during pregnancy, because more than half of them deemed it as a good hygiene practice, which to a larger extend disturbed the normal flora of the vagina predisposing them to BV. Douching has been known to cause disturbance of vaginal chemical balance and microbial normal flora hence leading to overgrowth of BV causing microorganisms 6. This finding is consistent with results from several other previous studies 17,18.
There was a significant association between BV and HIV infection. The current study noted a high prevalence of BV among HIV infected women. However the prevalence of HIV among the participants was less than 5% in the current study, therefore the results may not be representative of all the population. Studies done elsewhere in the world have also highlighted a significant association of BV with HIV infection 19, 20. This is probably due to the immunosuppression caused by HIV infection which predisposes the women to infections such as BV. On the other hand it has been noted that BV increases susceptibility to HIV infection. Therefore interventions to reduce the occurrence of BV may have an impact on the spread of HIV at a population level.
Women with a history of STI were noted to have a two-fold increased risk of getting BV as compared to women who had no STI. This finding is consistent with a study done among pregnant Danish women where by women with a history of STI such as Neisseria gonorrhea and Chlamydia trachomatis had an increased risk of getting BV as compared to women who did not have any STI 21. This was also noted in another study done in England, where women with bacterial STI had a higher risk of getting BV 22. The association between STI and BV could presumably be due to high risk sexual behavior such as multiple sexual partners among these women. Although having previously experienced the symptoms of STI may make them more aware of vaginal abnormalities and thus seek treatment earlier.
The current study found that having more than one LTSP significantly increased the risk of getting BV. This finding is consistent with other previous studies 23,24. In the current study a significant relationship between more than one LTSP and BV was established as more than three quarters of the participants had more than one LTSP. In comparison most of the studies done to establish the association of LTSP and BV have been done on non- pregnant women, this is one of the few studies to do so in pregnancy. It has been suggested that increased number of LTSP predisposes to BV by causing the vaginal flora to become unstable 25. Changes in the vaginal environment induced by sexual intercourse with a new partner may increase susceptibility to abnormal colonization in certain women due to disruption of the woman’s already established vaginal flora. Coitus alters the physiochemical vaginal environment thereby also affecting the vaginal microflora. In particular, it has been shown that the alkaline prostatic content of the ejaculate raises the vaginal pH, which favors growth of the anaerobes 4,26.
Early age of sexual debut before 18 years was found to be significantly associated with BV. This finding is consistent with a study done in Zimbabwe, where by sexual debut before the age of 20 years was found to be the strongest predictor of vaginal infections 9. The reason for this is not quite clear however it could be presumed that women who have an early sexual debut are likely to be more sexually active or have more sexual partners. In addition immaturity of the genital tract which in not fully mature and is more susceptible to vaginal infection.
The major strength of the current study was that it was conducted in the largest tertiary care hospital in Dar es Salaam and therefore included participants from most parts of Dar es Salaam. The strength is also based on the large sample size. The limitation of this study was that self-reported risk behaviors and history of STI may have been under reported due to social acceptability. Despite this limitation, the data is reliable and can be used as proxy to predictors of BV among pregnant women.