Longitudinal assessment of bacterial vaginosis prior to and during incident pregnancy: an observational study in Kenyan adolescent girls and young women

Abstract

Objective

To determine bacterial vaginosis (BV) status at multiple time points among adolescent girls and young women (AGYW) and assess the impact of pregnancy on their BV status.

Design

Longitudinal cohort study.

Setting

Thika, Kenya.

Participants

AGYW aged 16–20 years enrolled prior to first sex or reporting only a single lifetime partner.

Main outcome measures

The primary outcome was relative risk (RR) of BV during pregnancy compared with before pregnancy by analysing longitudinal trends in BV over time. BV risk was estimated using Poisson regression models.

Results

A total of 121 AGYW became pregnant in the parent cohort and had BV results before, during or after pregnancy. Point prevalence of BV was 11.0% at visits >12 months pre-pregnancy, 13.0% at 3–12 months pre-pregnancy, 22.1% at <3 months pre-pregnancy and 13.4% during pregnancy. Compared with visits during pregnancy, RR of BV was 1.65 (95% CI: 1.00 to 2.71; p=0.05) at visits <3 months pre-pregnancy, 0.97 (95% CI: 0.62 to 1.52; p=0.90) at visits 3–12 months pre-pregnancy and 0.82 (95% CI: 0.44 to 1.53; p=0.53) at visits 12 months pre-pregnancy. An adjusted analysis including age, income, residence, date of first sex, recent sexual activity and positive sexually transmitted infection test resulted in small changes in risk estimates, with adjusted RR of BV of 1.66 (95% CI: 1.04 to 2.67; p=0.04) at visits <3 months pre-pregnancy compared with visits during pregnancy.

Conclusions

BV risk during pregnancy was lower than during the immediate pre-pregnancy period. Hormonal changes in pregnancy may reduce BV.

Correspondence to Dr Lynda Oluoch; [email protected]

STRENGTHS AND LIMITATIONS OF THIS STUDY

• Our study uses longitudinal data and includes pre-pregnancy specimens, enabling detailed observations of changes in bacterial vaginosis (BV) status over time.

• This study provides novel information about BV changes among young women, a priority population for improving reproductive health; most prior data come from older women.

• Limitations of the study include self-report of dates including last menstrual period, menarche and first sex.

• Our study population was from a suburban area of Kenya and included adolescent girls and young women (AGYW) with first sex after age 16 years, and the results may not be generalisable to other AGYW in other settings or with younger age at first sex.

Introduction

Bacterial vaginosis (BV) is a prevalent vaginal condition characterised by a shift from a vaginal microbiota dominated by Lactobacillus spp to a microbiota with elevated levels of diverse anaerobic species.¹ The aetiology of BV is multifactorial, including risk factors such as sexual activity, condomless sex, new sexual partners, vaginal washing, douching with commercial products, menses and presence of sexually transmitted infections (STIs) implicated.^2–4

BV is the most common cause of vaginal discharge and inflammation in women of reproductive age globally,^5–7 and one meta-analysis estimated burden of BV in sub-Saharan Africa of 25%.⁵ Notably, African women also exhibit a lower prevalence of protective Lactobacillus spp compared with white and Asian American women.^{8 9}

Existing research on BV prevalence in Africa has largely been cross-sectional, with limited understanding of longitudinal BV dynamics.^{8 9} Numerous studies have highlighted the significant association between BV and increased risk of HIV acquisition among African women.^{5–7 10 11} In Kenya, 35% of newly reported infections in 2020 were attributed to young people (15–24 years), of which two-thirds of cases were identified among young females.^{12 13} A South African study of sexually active adolescent girls and young women (AGYW) revealed that diverse vaginal microbiota was common, with only 37% in this study found to have a microbiome dominated by lactobacilli.¹⁴ Moreover, the presence of diverse vaginal microbiome was correlated with higher levels of inflammatory cytokines, which may further increase the risk of HIV acquisition.^{14 15} Since BV may explain some of the vulnerability of AGYW to HIV acquisition, it is important to determine when AGYW demonstrate BV and what factors are involved in BV incidence and prevalence.

BV in pregnancy increases the risk of adverse outcomes including preterm births, miscarriages, chorioamnionitis and low birth weight.^16–18 It is hypothesised that vaginal dysbiosis at preconception is more likely to cause adverse pregnancy outcomes as opposed to vaginal dysbiosis during the pregnancy.¹⁹ Given the high BV prevalence among African women, it is important to understand BV changes with pregnancy. There is a scarcity in data published that focus solely on AGYW and BV trends from first sex to pregnancy occurrence, with little understanding of longitudinal pregnancy-induced changes to BV status among AGYW who become pregnant. One approach that could be used to understand BV over time in AGYW would be to examine longitudinal cohort data. We conducted a secondary analysis of data from a cohort of Kenyan AGYW enrolled prior to sexual debut or with a single lifetime partner.^{20 21} We assessed BV status at multiple time points and investigated the associations of pregnancy on risk of BV occurrence among AGYW.

Methods

Study setting, population and design

Our study was a nested analysis conducted within the Girls’ Health Study (GHS) which was conducted between 2014 and 2020 at the Partners in Health Research and Development Kenya Medical Research Institute research clinic in Thika, Kenya. The GHS was a prospective cohort designed to investigate factors associated with STI acquisition among young African women. To be eligible for enrolment, participants had to be aged 16–20 years, sexually naive or reporting one lifetime sexual partner by self-report, HIV 1 and herpes simplex virus 2 (HSV-2) seronegative, and willing to undergo genital examination at the clinic every 3 months.

AGYW aged 16–20 years were recruited from the general community and colleges. Our previous experience in enrolling AGYW was used, and we employed health talks in churches, schools and middle-level colleges as a recruitment strategy. Similarly, we used a community-based approach to provide education on reproductive health. This involved engaging with parents and girls in the community, focusing on STIs and reproductive health. Our educational message was delivered in a culturally sensitive manner with prior approval sought from community opinion leaders.

For this substudy, we analysed data from the parent cohort. We identified sexually active participants from the parent cohort and confirmed those who were pregnant during follow-up. Pregnancies without proper dating or BV data were excluded from analysis.

Study procedures

Written informed consent was obtained from participants 18 years of age and older. For participants younger than 18 years of age, written informed consent was obtained from their guardians, and participants provided written informed assent.

Participants were followed on a quarterly basis and underwent genital examinations. Vaginal swabs were collected and assessed using Gram stain to determine presence of BV. Gram stain was graded according to the Nugent scoring system.²² Testing for STIs was conducted annually and in response to symptoms or signs of STIs, for example, genital sores, genital discharge or itching in the genital area. Nucleic acid amplification testing (NAAT) of genital swabs was performed to detect Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT) and Trichomonas vaginalis (TV) using the Gen-Probe APTIMA test (Hologic, Marlborough, MA). Serum ELISA assays were used for HIV testing (Vironostika HIV Uni-Form II Ag-Ab (Biomerieux, Marcy-l’Etoile, France)) and HSV-2 testing (HerpeSelect HSV-2 ELISA test (Focus Diagnostics, Cypress, California, USA)) with confirmation by HSV western blot.²³

Data collection

Demographic data, medical history and sexual reproductive health history, such as the timing of first sex, number of sexual partners, frequency of sex, consistency of condom use, history of vaginal discharge and STI diagnoses, were collected and recorded in REDCap.²⁴ Sexual activity was defined as penile–vaginal penetrative intercourse. Participants who reported being sexually active and not using any contraception received contraceptive counselling.

The last menstrual period (LMP) of participants was recorded at every visit, and pregnancy testing was conducted upon request or when participants reported a missed LMP. If a pregnancy test was positive, participants were linked to appropriate care. Pregnant participants were encouraged to continue with quarterly visits, although some opted out of genital examinations during pregnancy. Only first pregnancies were included in the analysis, which encompasses visits both prior to and during the first pregnancy.

Statistical analysis

The parent study was powered to observe HSV-2 acquisition. Based on HSV-2 prevalence data,²⁵ projected incidence of 7.8% per year and a median age of first sex of 18 years,²⁶ we assumed that enrolling 400 HSV-2-seronegative persons would result in 73 observed HSV-2 acquisitions, accounting for 13% dropout. For our nested study, we sampled all participants who reported incident pregnancy during study follow-up and included participants who had at least one BV result.

The main exposure variable categorised visits as: during pregnancy, <3 months before pregnancy to observe the immediate pre-pregnancy period, 3–12 months before pregnancy to ensure that all participants had at least one study visit during this period and >12 months before pregnancy. BV diagnosis was defined as Nugent score of ≥7 from vaginal Gram stain analysis. Descriptive statistics were used to describe baseline and follow-up characteristics of the AGYW cohort. Multivariate regression models using generalised estimating equations (GEE) were used to analyse longitudinal trends in BV over time, and to examine correlates of risk of BV during pregnancy compared with before pregnancy.²⁷ Treating presence of BV as a binary outcome, the relative risk (RR) of BV pre-pregnancy, compared with during pregnancy, was estimated using a Poisson model with independent working correlation and robust SEs. Models were adjusted for covariates including recent sex and history of STI. Statistical analysis was performed using Stata V.16.0.²⁸

Patient and public involvement

Research questions were not formulated with community input. Community opinion leaders were sensitised to the study topics and provided advice on appropriate ways to approach girls and their parents during the recruitment process. A Community Advisory Board (CAB) was consulted about the study as it was being planned. Result dissemination activities were held during years 1 and 2 of the study. These activities included presentations to relevant stakeholders in the CAB, aimed at sharing preliminary findings from the parent study and building awareness about its progress. In addition to the activities conducted in the initial years, we do indeed plan to further disseminate the study results, including those presented in this report. One of our foremost dissemination goals is the publication of the study results in a reputable, peer-reviewed journal. This will enable us to contribute to the academic discourse, ensure the accessibility of our findings to a wider audience and allow for constructive feedback from experts in the field.

Results

Study cohort characteristics

The parent study screened 610 AGYW, and 400 were enrolled.^{20 21} The median age of participants at enrolment was 18.6 years (IQR: 17.6–19.4) and the median years of schooling was 12 (IQR: 10–12). At enrolment, 322 participants (80.5%) reported no history of sex, while 78 (19.5%) reported one lifetime sexual partner. The median follow-up time for participants was 51 months (IQR: 27–57). A total of 127 first pregnancies were reported during study follow-up (figure 1).

Figure 1. (A) Flow diagram demonstrating eligible pregnant participants with incident pregnancy and their BV test results (N=121). (B) Nugent score results for 121 pregnant study participants. BV, bacterial vaginosis.

BV prevalence over time

Of 127 pregnancies in nulliparous participants, 121 pregnancies were included in this analysis; two pregnancies lacked a pregnancy start date, one was excluded after HIV diagnosis and three pregnancies occurred in participants with no BV data. Among the 121 pregnant AGYW, 94% had BV testing pre-pregnancy, while 87% had BV testing during pregnancy (figure 1A).

Of 116 participants who contributed visits pre-pregnancy, 87 participants were seen 12 months or more pre-pregnancy, 110 participants contributed visits in the 3–12 months pre-pregnancy, 91 participants contributed visits <3 months pre-pregnancy and 105 participants contributed visits during pregnancy. In total, 926 Nugent scores were available at these time points (figure 1B). Among all pre-pregnancy visits, the prevalence of BV was 13.2%. The point prevalence of BV was 11.0% among visits >12 months pre-pregnancy, 13.0% among visits 3–12 months pre-pregnancy, 22.1% among visits <3 months pre-pregnancy and 13.4% during pregnancy.

Correlates of BV among pregnant participants

A GEE analysis of key biological and behavioural factors was performed modelling risk of BV in the 121 women with pregnancy specimens. This model demonstrated multiple factors correlated with RR of BV event over time. Overall, compared with during pregnancy, risk of BV was higher <3 months before pregnancy with an adjusted RR (aRR) of 1.66 (95% CI: 1.04, 2.67; p=0.04). The factor most significantly associated with BV risk was HSV-2 infection (aRR 3.80, 95% CI 1.71 to 8.42, p=0.001), followed by NG (aRR 2.35, 95% CI 1.25 to 4.45, p=0.01). There were also non-significant trends toward increased risk for those reporting sex in last 90 days, those with CT and those living in an urban setting (table 1). Factors that were not associated with increased risk of BV included age, income, and time between menarche and first intercourse.

Table 1

Relative risk (RR) for bacterial vaginosis among adolescent girls and young women who became pregnant (N=121)

Bacterial vaginosis diagnosis	Unadjusted			Adjusted
	RR	95% CI	P value	aRR	95% CI	P value
Time
During pregnancy	Referent			Referent
<3 months prior to pregnancy	1.65	1.00 to 2.71	0.05	1.66	1.04 to 2.67	0.04
3–12 months prior to pregnancy	0.97	0.62 to 1.52	0.90	1.07	0.65 to 1.76	0.78
>12 months prior to pregnancy	0.82	0.44 to 1.53	0.53	1.04	0.53 to 2.06	0.91
Older age at visit, years	1.01	0.85 to 1.19	0.94	0.95	0.76 to 1.18	0.65
Residence
Rural	Referent			Referent
Urban	1.63	0.94 to 2.84	0.08	1.75	0.94 to 3.25	0.08
Income, per month
>1000 KES	Referent			Referent
1–1000 KES	1.06	0.30 to 3.75	0.92	1.53	0.38 to 6.10	0.55
No regular income	1.57	0.57 to 4.35	0.38	2.14	0.64 to 7.12	0.22
Menarche to first sex
>5 years	Referent			Referent
3–4.9 years	1.32	0.66 to 2.65	0.43	1.19	0.61 to 2.31	0.61
<3 years	1.10	0.51 to 2.38	0.80	0.88	0.43 to 1.79	0.73
History of sex
No sex in past 90 days	Referent			Referent
Sex in past 90 days	1.80	1.02 to 3.19	0.04	1.59	0.93 to 2.69	0.09
CT infection
CT negative	Referent			Referent
CT positive	1.86	1.15 to 3.00	0.01	1.48	0.96 to 2.26	0.08
NG infection
NG negative	Referent			Referent
NG positive	2.60	1.24 to 5.45	0.01	2.35	1.25 to 4.45	0.01
HSV-2 serostatus
HSV-2 seronegative	Referent			Referent
HSV-2 seropositive	2.33	0.97 to 5.59	0.06	3.80	1.71 to 8.42	0.001

Poisson regression using generalised estimating equations was used to analyse longitudinal trends in bacterial vaginosis. The adjusted analysis included adjustment for time-fixed covariates (urban residence, monthly income, and years between menarche and first sex) and time-varying covariates (length of time between study visit and onset of pregnancy; age at study visit; history of sex in the past 90 days; and CT, NG and HSV-2 infection).

97 KES was equivalent to US$1 at the time of data collection.

aRR, adjusted RR; CT, Chlamydia trachomatis; HSV-2, herpes simplex virus type 2; KES, Kenya shillings; NG, Neisseria gonorrhoeae.

Since BV is associated with sexual activity, we compared reported sexual activity at pregnancy (69% of visits) with pre-pregnancy (29% of visits >12 months pre- pregnancy, 48% of visits 3–12 months pre-pregnancy and 53% of visits <3 months pre-pregnancy). Sexual activity was reported more commonly by AGYW while pregnant compared with any pre-pregnancy time point.

Discussion

Using longitudinal cohort data with a 3-month sampling interval, our study investigated changes in the frequency of vaginal dysbiosis in AGYW who became pregnant for the first time. We observed a lower prevalence of BV during pregnancy compared with the months immediately pre-pregnancy. We also noted that RR of BV diagnosis during pregnancy was 34% lower than <3 months prior to pregnancy, even after controlling for known cofactors such as sexual activity and STIs.^{2 3} This observation adds to the literature on BV in pregnancy by focusing on younger women. Prior studies on BV and pregnancy have focused on adverse outcomes associated with BV during and after pregnancy,^{17 29–32} and our study provides novel insights by examining changes in BV status prior to and during the initial pregnancy.

Most published studies on longitudinal patterns of BV have sampled older and more sexually experienced women or AGYW who were more sexually active.^33–35 Our study, on the other hand, provides a new perspective by investigating AGYW at the start and early stages of their sexual lives. Additionally, our study is distinct due to the longitudinal collection of specimens, including pre-pregnancy samples from different time points, which is not commonly done in other studies on BV and pregnancy.

BV is considered undesirable in pregnancy as it has been linked to multiple adverse pregnancy outcomes, including preterm births, miscarriages, chorioamnionitis and low birth weight.^{36 37} Vaginal dysbiosis at preconception may be more likely to cause infertility compared with vaginal dysbiosis during pregnancy.¹⁹ Previous studies from small cohorts in the Americas and Europe have noted differences in the vaginal environment between pregnant and non-pregnant women showing less diversity and enrichment of Lactobacillus spp, which are known to be protective against BV.^{38 39} Studies of contraceptive vaginal rings demonstrated that oestrogen enhances an optimal lactobacilli-dominated vaginal microbial community.⁴⁰ Production of oestrogen during pregnancy is associated with increase in concentration of protective lactobacilli species.^{41 42} Thus, a possible explanation for our results is that the elevated oestrogen environment during pregnancy may promote a more optimal vaginal environment. Another possible explanation is that pregnant women do not menstruate, and menses are linked to BV. However, the risk of BV during pregnancy was the same as among menstruating women >3 months prior to pregnancy.

Few studies have captured BV trends in AGYW from first sex to pregnancy occurrence, limiting understanding of how pregnancy may influence changes in BV status among AGYW.^{8 9} This study’s longitudinal approach enables the elucidation of modifiable factors, which could reduce BV during pregnancy. Our study identified an association between BV and HSV-2 and CT infections which is consistent with previous studies.^43–45 The short time interval observed between first sexual activity, first STI and first pregnancy in our study may have resulted in concurrent occurrences of these events, which may have influenced our findings. To improve pregnancy outcomes and reduce BV, availability of BV and STI diagnostics is an important barrier to progress. Our study used Nugent scoring to diagnose BV, NAAT to diagnose CT and serum ELISA to diagnose HSV-2; none of these diagnostics are routinely available in low-resource settings for pregnant populations.^46–48

Our study had some limitations. Multiple key variables were collected by self-report including dates of LMP, menarche and first sex. To improve accuracy, we amended the date of sexual activity if STI or pregnancy results indicated that sexual activity had occurred, and we also included retrospective reporting by participants. Participants were slightly more likely to refuse genital sample collection during pregnancy, which could result in bias. However, specimens were collected from over 80% of pregnant women, which should be adequate representation. Vaginal washing data were missing for many participants and we were unable to assess the association between vaginal washing and BV in this cohort.

Conclusion

Our study presents a longitudinal assessment of BV in AGYW from the pre-pregnancy period to incident pregnancy. Pregnant AGYW were noted to have lower risk of BV diagnoses during pregnancy compared with the immediate pre-pregnancy period. Pregnancy appears to be a time of lower risk of BV in these young women, for reasons that may relate to the hormonal milieu. Further molecular characterisation of vaginal bacteria and biological factors that drive vaginal dysbiosis will be analysed from this study to understand whether other modifiable risk factors can be identified to reduce BV risk during pregnancy.

Data availability statement

Data are available upon reasonable request. De-identified data from the study will be available immediately after publication, with no end date via reasonable request to the corresponding author at [email protected]. Data containing identifiers will require the concurrence of the KEMRI Scientific and Ethical Review Committee (https://www.kemri.go.ke/scientific-ethics-review-unit-seru).

Ethics statements

Patient consent for publication

Not required.

Ethics approval

This study involves human participants and ethics approval was obtained from the University of Washington (UW) Human Subjects Division (reference number/ID: 46577) and Scientific Ethics Review Unit (KEMRI-SERU; reference number/ID: 2760). Participants gave informed consent to participate in the study before taking part.

Footnote

Twitter @oluocl, @RoxbyMD

Contributors All the listed authors' contributions include the conception and design, acquisition of data or analysis and interpretation of data, drafting the article or revising it critically for important intellectual content, and final approval of the version published. Regarding responsibility for overall content, the lead author, LO, is the guarantor. LO had the idea for this article and wrote the first draft. AR, KT, KN, AW and NM wrote additional sections. LS, CK, EC, SGM, LM, SS, MW and BC suggested additional changes. All authors revised the article and approved the final version. As the guarantor, LO affirms that the manuscript provides an honest, accurate and transparent account of the issues covered, that there are no important omissions, and that there are no discrepancies between what was planned and the final version. All authors accept full responsibility for the work and the decision to publish.

Funding This research was funded by R01 HD091996-01 (ACR) from NICHD, by P01 AI 030731 (AW) and by the University of Washington/Fred Hutch, Center for AIDS Research (CFAR; AI027757). LO was a scholar in the International AIDS Research and Training Program, supported by the Fogarty International Center and National Institutes of Health (NIH) Research Grant (D43 TW009783). Study data were collected and managed using REDCap electronic data capture tools hosted at the University of Washington funded by UL1 TR002319, KL2 TR002317 and TL1 TR002318 from NCATS/NIH.

Disclaimer The funders had no role in study design, data collection and analysis, or preparation of the manuscript. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Competing interests None declared.

Patient and public involvement Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods section for further details.

Provenance and peer review Not commissioned; externally peer reviewed.

References

¹ Muzny CA, Taylor CM, Swords WE, et al. An updated conceptual model on the pathogenesis of bacterial Vaginosis. J Infect Dis 2019; 220: 1399–405. doi:10.1093/infdis/jiz342

² Ranjit E, Raghubanshi BR, Maskey S, et al. Prevalence of bacterial Vaginosis and its association with risk factors among Nonpregnant women: a hospital-based study. Int J Microbiol 2018; 2018: 8349601. doi:10.1155/2018/8349601

³ Haydar SO, Naqid I. A study of bacterial Vaginosis and associated risk factors among married women in Zakho city, Kurdistan region, Iraq. JLBSR 2022; 3: 33–9. doi:10.38094/jlbsr30262

⁴ McClelland RS, Lavreys L, Hassan WM, et al. Vaginal washing and increased risk of HIV-1 acquisition among African women: a 10-year prospective study. AIDS 2006; 20: 269–73. doi:10.1097/01.aids.0000196165.48518.7b

⁵ Peebles K, Velloza J, Balkus JE, et al. High global burden and costs of bacterial Vaginosis: a systematic review and meta-analysis. Sex Transm Dis 2019; 46: 304–11. doi:10.1097/OLQ.0000000000000972

⁶ Torrone EA, Morrison CS, Chen P-L, et al. Prevalence of sexually transmitted infections and bacterial Vaginosis among women in sub-Saharan Africa: an individual participant data meta-analysis of 18 HIV prevention studies. PLoS Med 2018; 15: e1002608. doi:10.1371/journal.pmed.1002608

⁷ Bagnall P, Rizzolo D. Bacterial Vaginosis: a practical review. JAAPA 2017; 30: 15–21. doi:10.1097/01.JAA.0000526770.60197.fa

⁸ Jespers V, Kyongo J, Joseph S, et al. A longitudinal analysis of the vaginal Microbiota and vaginal immune mediators in women from sub-Saharan Africa. Sci Rep 2017; 7: 11974. doi:10.1038/s41598-017-12198-6

⁹ Gautam R, Borgdorff H, Jespers V, et al. Correlates of the molecular vaginal Microbiota composition of African women. BMC Infect Dis 2015; 15: 86. doi:10.1186/s12879-015-0831-1

¹⁰ Bayigga L, Kateete DP, Anderson DJ, et al. Diversity of vaginal Microbiota in sub-Saharan Africa and its effects on HIV transmission and prevention. Am J Obstet Gynecol 2019; 220: 155–66. doi:10.1016/j.ajog.2018.10.014

¹¹ Dabee S, Barnabas SL, Lennard KS, et al. Defining characteristics of genital health in South African adolescent girls and young women at high risk for HIV infection. PLoS One 2019; 14: e0213975. doi:10.1371/journal.pone.0213975

¹² UNAIDS. Global HIV & AIDS statistics — fact sheet. Available: https://www.unaids.org/en/resources/fact-sheet [Accessed 12 Sep 2022 ].

¹³ UNICEF Kenya. HIV and AIDS. 2020. Available: https://www.unicef.org/kenya/hiv-and-aids

¹⁴ van de Wijgert JHHM. The vaginal Microbiome and sexually transmitted infections are interlinked: consequences for treatment and prevention. PLoS Med 2017; 14: e1002478. doi:10.1371/journal.pmed.1002478

¹⁵ Anahtar MN, Byrne EH, Doherty KE, et al. Cervicovaginal bacteria are a major modulator of host inflammatory responses in the female genital tract. Immunity 2015; 42: 965–76. doi:10.1016/j.immuni.2015.04.019

¹⁶ Bhakta V, Aslam S, Aljaghwani A. Bacterial Vaginosis in pregnancy: prevalence and outcomes in a tertiary care hospital. Afr J Reprod Health 2021; 25: 49–55. doi:10.29063/ajrh2021/v25i1.6

¹⁷ Mulinganya G, De Vulder A, Bisimwa G, et al. Prevalence, risk factors and adverse pregnancy outcomes of second trimester bacterial Vaginosis among pregnant women in Bukavu, democratic Republic of the Congo. PLoS One 2021; 16: e0257939. doi:10.1371/journal.pone.0257939

¹⁸ Kamga YM, Ngunde JP, Akoachere J-F. Prevalence of bacterial Vaginosis and associated risk factors in pregnant women receiving Antenatal care at the Kumba health district (KHD), Cameroon. BMC Pregnancy Childbirth 2019; 19: 166. doi:10.1186/s12884-019-2312-9

¹⁹ Lokken EM, Manhart LE, Kinuthia J, et al. Association between bacterial Vaginosis and Fecundability in Kenyan women planning pregnancies: a prospective Preconception cohort study. Hum Reprod 2021; 36: 1279–87. doi:10.1093/humrep/deab002

²⁰ Wang M, Tapia K, Oluoch LM, et al. Adolescent girls and young women in Kenya demonstrate rapid STI incidence following first sex: data from a longitudinal cohort. J Adolesc Health 2023; 72: 568–74. doi:10.1016/j.jadohealth.2022.10.026

²¹ Xiao Y, Zhang Y, Sun Y, et al. Does green space really matter for residents' obesity? A new perspective from Baidu street view. Front Public Health 2020; 8: 332. doi:10.3389/fpubh.2020.00332

²² Nugent RP, Krohn MA, Hillier SL. Reliability of diagnosing bacterial Vaginosis is improved by a standardized method of gram stain interpretation. J Clin Microbiol 1991; 29: 297–301. doi:10.1128/jcm.29.2.297-301.1991

²³ Ashley RL, Militoni J, Lee F, et al. Comparison of Western blot (Immunoblot) and glycoprotein G-specific Immunodot enzyme assay for detecting antibodies to herpes Simplex virus types 1 and 2 in human sera. J Clin Microbiol 1988; 26: 662–7. doi:10.1128/jcm.26.4.662-667.1988

²⁴ Harris PA, Taylor R, Thielke R, et al. Research electronic data capture (Redcap)–A Metadata-driven methodology and Workflow process for providing Translational research Informatics support. J Biomed Inform 2009; 42: 377–81. doi:10.1016/j.jbi.2008.08.010

²⁵ Mugo N, Dadabhai SS, Bunnell R, et al. Prevalence of herpes Simplex virus type 2 infection, human immunodeficiency virus/herpes Simplex virus type 2 Coinfection, and associated risk factors in a national, population-based survey in Kenya. Sex Transm Dis 2011; 38: 1059–66. doi:10.1097/OLQ.0b013e31822e60b6

²⁶ Ndayisaba G, Verwijs MC, van Eeckhoudt S, et al. Feasibility and acceptability of a novel Cervicovaginal Lavage self-sampling device among women in Kigali, Rwanda. Sex Transm Dis 2013; 40: 552–5. doi:10.1097/OLQ.0b013e31828e5aa5

²⁷ Wang M. Generalized estimating equations in longitudinal data analysis: a review and recent developments. Advances in Statistics 2014; 2014: 1–11. doi:10.1155/2014/303728

²⁸ StataCorp. Stata Statistical Software: Release 16. College Station, TX: StataCorp LLC, 2019.

²⁹ Aduloju OP, Akintayo AA, Aduloju T. Prevalence of bacterial Vaginosis in pregnancy in a tertiary health institution, South Western Nigeria. Pan Afr Med J 2019; 33: 9.: 9. doi:10.11604/pamj.2019.33.9.17926

³⁰ Sule-Odu AO, Oluwole AA, Akadri AA, et al. Bacterial Vaginosis in pregnancy and early labour using Nugent scoring and the implication on foetal outcome. Ghana Med J 2020; 54: 10–6. doi:10.4314/gmj.v54i1.3

³¹ Juliana NCA, Suiters MJM, Al-Nasiry S, et al. The association between vaginal Microbiota Dysbiosis, bacterial Vaginosis, and aerobic Vaginitis, and adverse pregnancy outcomes of women living in sub-Saharan Africa: A systematic review. Front Public Health 2020; 8: 567885. doi:10.3389/fpubh.2020.567885

³² Tedesco RP, Galvão RB, Guida JP, et al. The role of maternal infection in Preterm birth: evidence from the Brazilian Multicentre study on Preterm birth (EMIP). Clinics (Sao Paulo) 2020; 75: e1508. doi:10.6061/clinics/2020/e1508

³³ Afolabi BB, Moses OE, Oduyebo OO. Bacterial Vaginosis and pregnancy outcome in Lagos, Nigeria. Open Forum Infect Dis 2016; 3: ofw030. doi:10.1093/ofid/ofw030

³⁴ Coudray MS, Sheehan DM, Li T, et al. Factors associated with the recurrence, persistence, and clearance of asymptomatic bacterial Vaginosis among young African American women: A repeated-measures latent class analysis. Sex Transm Dis 2020; 47: 832–9. doi:10.1097/OLQ.0000000000001256

³⁵ Peebles K, Kiweewa FM, Palanee-Phillips T, et al. MTN-020/ASPIRE study team. elevated risk of bacterial Vaginosis among users of the copper Intrauterine device: A prospective longitudinal cohort study. Clin Infect Dis 2021; 73: 513–20. doi:10.1093/cid/ciaa703

³⁶ Shimaoka M, Yo Y, Doh K, et al. Association between Preterm delivery and bacterial Vaginosis with or without treatment. Sci Rep 2019; 9: 509. doi:10.1038/s41598-018-36964-2

³⁷ Brabant G. Bacterial Vaginosis and spontaneous Preterm birth. J Gynecol Obstet Biol Reprod (Paris) 2016; 45: 1247–60. doi:10.1016/j.jgyn.2016.09.014

³⁸ Romero R, Hassan SS, Gajer P, et al. The composition and stability of the vaginal Microbiota of normal pregnant women is different from that of non-pregnant women. Microbiome 2014; 2: 4. doi:10.1186/2049-2618-2-4

³⁹ Freitas AC, Chaban B, Bocking A, et al. The vaginal Microbiome of pregnant women is less rich and diverse, with lower prevalence of Mollicutes, compared to non-pregnant women. Sci Rep 2017; 7: 9212. doi:10.1038/s41598-017-07790-9

⁴⁰ Balle C, Gill K, Konstantinus IN, et al. Hormonal contraception and risk of Stis and bacterial Vaginosis in South African adolescents: secondary analysis of a randomised trial. Sex Transm Infect 2021; 97: 112–7. doi:10.1136/sextrans-2020-054483

⁴¹ Odogwu NM, Onebunne CA, Chen J, et al. Lactobacillus Crispatus thrives in pregnancy hormonal milieu in a Nigerian patient cohort. Sci Rep 2021; 11: 18152. doi:10.1038/s41598-021-96339-y

⁴² Donders GGG. Reducing infection-related Preterm birth. BJOG 2015; 122: 219. doi:10.1111/1471-0528.13109

⁴³ Shipitsyna E, Khusnutdinova T, Budilovskaya O, et al. Bacterial Vaginosis-associated vaginal Microbiota is an age-independent risk factor for Chlamydia Trachomatis, Mycoplasma Genitalium and trichomonas vaginalis infections in low-risk women. Eur J Clin Microbiol Infect Dis 2020; 39: 1221–30. doi:10.1007/s10096-020-03831-w

⁴⁴ Tamarelle J, Thiébaut ACM, de Barbeyrac B, et al. The vaginal Microbiota and its association with human Papillomavirus, Chlamydia Trachomatis, Neisseria Gonorrhoeae and Mycoplasma Genitalium infections: a systematic review and meta-analysis. Clin Microbiol Infect 2019; 25: 35–47. doi:10.1016/j.cmi.2018.04.019

⁴⁵ Brotman RM, Bradford LL, Conrad M, et al. Association between trichomonas vaginalis and vaginal bacterial community composition among reproductive-age women. Sex Transm Dis 2012; 39: 807–12. doi:10.1097/OLQ.0b013e3182631c79

⁴⁶ Bosu WK. Syndromic management of sexually transmitted diseases: is it rational or scientific Trop Med Int Health 1999; 4: 114–9. doi:10.1046/j.1365-3156.1999.00360.x

⁴⁷ Vuylsteke B. Current status of Syndromic management of sexually transmitted infections in developing countries. Sex Transm Infect 2004; 80: 333–4. doi:10.1136/sti.2004.009407

⁴⁸ White RG, Moodley P, McGrath N, et al. Low effectiveness of Syndromic treatment services for Curable sexually transmitted infections in rural South Africa. Sex Transm Infect 2008; 84: 528–34. doi:10.1136/sti.2008.032011