A comparison among different regions in Africa was made by Prevalence of BV among pregnant women. However, there were many factors that hampered comparisons among different studies (HIV positive or negative, symptomatic or asymptomatic and test method used). Despite these difficulties, cumulative prevalence within the same country or across country and comparison based on the same test method was conducted in this review. Generally, the prevalence of BV among pregnant women was considerably higher in the African continent.
This review addressed the prevalence of BV and its associated risk factors among pregnant women and its associated risk factors conducted in 31 eligible studies from 15 different countries of Africa, in which most of the studies are from Nigeria 22.6% (7/31), Kenya 16% (5/31) and Ethiopia 13% (4/31)(Table 1).
Samples from a total of 19,354 pregnant women and from all 31 eligible studies from January 2008 to December 2018, 4795 were positive for BV with the overall prevalence of 24.8% (4795/19,354) (Table 1), with the highest cumulative prevalence was reported from two studies conducted in more than two countries in Africa (1113/2349, 47.4%) and high among HIV infected pregnant women, 1096/2292, 47.8%)[12, 23] and followed by Southern regions of Africa (826/2136, 38.7%) with the highest prevalence from Zambia (524/1084, 48.3%) .
The majority of the studies were from the East Africa region (13/31, 41.9%), while the smallest number of studies were from the Northern African region (1/31, 3.2%) (Table 1). No suitable report was obtained from the region of central Africa. Most of the studies (15/31, 48.4%) were cross-sectional studies, and almost all studies (24/31, 77.4%) are diagnosed using the Nugent scoring system. Individually, the highest prevalence of BV (60%) was reported from Nigeria, the western region of Africa, among symptomatic pregnant women using Nugent score whereas the lowest prevalence was reported from Uganda, the eastern region of Africa, among pregnant women who are in the third trimester of pregnancy with all of them are negative for Nugent score 7–10 to classify as BV positive.
The prevalence of BV was generally high among HIV infected pregnant women as compared to HIV negative pregnant women, with the prevalence of 52%, 47.8%, 46%, 37%, 37%, 25% and 11.9% in which most of the studies were from Kenya and Nigeria.
The geographical distribution of BV among pregnant women in African countries shows that there was substantial difference in prevalence among different countries in Africa. For, example, studies conducted from eastern regions of Africa reported the highest prevalence of 52% from Kenya, which was followed by a study reported from Sudan, 49.8%. However, few studies from the eastern part of Africa also reported a very low prevalence of BV from studies reported especially from Uganda and Ethiopia. High prevalence of BV was reported not only from the eastern region but also from the western region (highest prevalence’s from Nigeria (56.6% and 60%)[10, 20] and Cameroon (45.8%)) and southern regions of Africa with the highest prevalence reported from Zambia 48.3%.
Risk factors significantly associated with BV were; HIV[11, 17, 27, 32, 36, 38] (Table 2), age [25, 29, 30], previous BV/STI [13, 20, 21], history of abortion [21, 26], number of LTSP [20, 26], gestational age  and douching . Whereas complications associated with BV were also Preterm delivery, Low birth weight, and premature rupture of membranes. Among pregnant women with a history of STI significantly associated with BV were; HSV-2, polygamist (multiple sexual partners), and genital ulcer. And women who used water for cleaning after visiting the toilet were vulnerable to BV as compared to those who used toilet paper or other solid means.
Pregnant women who had a history of abortion, especially spontaneous history of abortion and with the early stages of pregnancy, were at high risk of being BV positive and some studies indicated that women in the early stages of pregnancy and history of abortion were significantly associated with BV[21, 26, 32].