Abstract
Background
Maternal Group B Streptococcus (GBS) colonization is influenced by many factors but results are inconsistent. Consideration of antenatal risk factors may help inform decision making on GBS microbiological culture screening where universal screening is not standard of care. We sought to identify independent predictors of GBS colonization at 34–37 weeks gestation incorporating vaginal symptoms, perineal hygiene measures, sexual activity, and a potential novel factor, constipation.
Methods
In this prospective cross-sectional study, 573 women at 34–37 weeks gestation had an ano-vaginal swab taken and sent for selective culture for GBS. Women were asked about vaginal bleeding, discharge, irritation and candidiasis, antibiotic use during pregnancy, ano-vaginal hygiene practices such as douching and perineal cleansing after toileting, sexual intercourse related activities, and a potential novel factor for GBS carriage, constipation. Maternal basic demographics and obstetric-related characteristics were also collected. Bivariate analyses were performed to identify associates of GBS colonization. All variables with p < 0.05 found on bivariate analysis were then included into a model for multivariable binary logistic regression analysis to identify independent risk factors for GBS colonization.
Results
GBS colonization was found in 235/573 (41.0%) of participants. Twenty six independent variables were considered for bivariate analysis. Eight were found to have p < 0.05. Following adjusted analysis, six independent predictors of GBS colonization were identified: ethnicity, previous neonatal GBS prophylaxis, antenatal vaginal irritation, antibiotic use, recent panty liner use, and frequency of sexual intercourse. Vaginal discharge and perineal cleansing were not associated after adjustment. Recent douching and constipation were not associated on bivariate analysis.
Conclusion
The identification of independent predictors of GBS colonization in late pregnancy may inform the woman and care provider in their shared decision making for microbiological screening at 35–38 weeks gestation in locations where universal GBS screening is not standard of care.
Ethics oversight
This study was approved by the Medical Ethics Committee of University Malaya Medical Centre (UMMC) on August 9, 2022, reference number 2022328-11120.
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Discover the latest articles, news and stories from top researchers in related subjects.Introduction
Approximately 19·7 million pregnant women were estimated to have rectovaginal colonization with Group B streptococcus (GBS) in 2020 [1] with at least 409 thousand (95% confidence interval: 144–573 thousand) maternal/ fetal/ infant cases and 147 thousand (uncertainty range, 47–273 thousand) stillbirths and infant deaths annually [2]. The primary risk factor for neonatal GBS early-onset disease (EOD) is GBS colonization of the maternal genitourinary and gastrointestinal tracts. Approximately 50% of women who are colonized with GBS will transmit the bacteria to their newborns. In the absence of intrapartum antibiotic prophylaxis, 1–2% of those newborns will develop GBS EOD [3]. GBS EOD has 5.2% mortality and 7.4% disability rate [4].
Asymptomatic colonization rates of pregnant women with GBS in the vagina or rectum varies between 6.5% [5] and 43.6% [6]. Maternal GBS colonization is influenced by age [7, 8], parity [9, 10], ethnicity [10,11,12], body mass index [8, 10, 13,14,15], GBS colonization in previous pregnancy [16,17,18], vulvitis [11], presence of sexually transmitted diseases [11, 19, 20], sexual behavior [21, 22], tobacco use [11, 23, 24], antibiotic exposure in pregnancy [25, 26], diabetes [27,28,29,30,31,32,33,34], and healthcare worker occupation [35] but results were inconsistent.
Intrapartum antibiotic prophylaxis is recommended in the presence of previous neonate with GBS disease, positive screening culture in the last 5 weeks, GBS bacteriuria in pregnancy, known GBS positive result in a previous pregnancy and intrapartum preterm birth, membrane rupture > 18 h, and maternal fever ≥ 38 0C [3].
The American College of Obstetricians and Gynecologists recommends universal GBS screening between 36 + 0/7 and 37 + 6/7 weeks of gestation [3]. In contrast, the United Kingdom National Screening Committee recommended that routine screening using bacteriological culture or near-patient testing techniques should not be introduced into United Kingdom practice, citing very low GBS EOD rates and the large number of women that would be given intrapartum antibiotic prophylaxis with universal screening [4]. Universal GBS screening is not standard of care in our Malaysian practice.
Considering antenatal risk factors may help inform decision-making on GBS microbiological culture screening where universal screening is not the standard of care. We sought to identify independent risk factors of GBS colonization at 34–37 weeks gestation [4] incorporating vaginal symptoms and sexual activity, and also as potential novel factors, perineal hygiene measures and constipation.
Materials and methods
This is a prospective cross-sectional study, approved by the Medical Ethics Committee of University Malaya Medical Centre (UMMC) on August 9, 2022, reference number 2022328-11120. This study was conducted in UMMC with the first participant recruited on August 17, 2022 and the last on February 7, 2023. Women who attended the antenatal clinic for routine care in UMMC, Kuala Lumpur, Malaysia, were assessed for eligibility to be recruited into the study.
Inclusion criteria were pregnant women age at least 18 years old, pregnant at 34–37 weeks, and live fetus. We excluded women with retroviral disease, active vaginal bleeding, and prelabor membrane rupture.
Eligible women were approached, provided with the patient information sheet, and had verbal enquiries answered by the recruiting care provider. Written informed consent was obtained from the participants.
After recruitment, participants had the anovaginal swab collection for GBS culture and completed a self-reported questionnaire developed for this study (Supplementary Material 1) that included questions on vaginal bleeding, discharge, irritation, candidiasis, and antibiotic use during pregnancy, ano-vaginal hygiene such as douching, perineal cleansing after toileting, and sexual intercourse related activities. Functional chronic constipation was identified using the Rome IV criterion [36].
Care providers would swab the lower part of the vagina without inserting a speculum. The same swab was then inserted through the anal sphincter (endoanal), rotated two or three times, and placed into the culture medium. A single swab was used [4]. The culture medium used in this study is the non-nutritive transport medium (Amies media with or without charcoal) and the samples were sent to the UMMC laboratory on the same day for GBS selective culture. Women were informed of culture results and those with positive cultures for GBS were given intrapartum antibiotic prophylaxis.
Data for the impact size of our novel risk factors on GBS colonization is unknown. We made the assumption odds ratio was a generic 1.75 over the negative. Using the Chi-Square test (case-control) with alpha 0.05, beta 0.2, and baseline GBS carriage at 20%, assuming 1 to 1 ratio in dichotomization within the independent novel covariables and odds ratio of 1.75, 271 participants were needed in each half of the groups i.e., 542 in total.
Taking a baseline GBS carriage rate of 20%, the event rate is 0.20. Considering a 10 variables multivariable logistic regression analysis, utilizing the rule of at least 10 cases/events, 100 GBS carriers are needed which should be found in 500 participants. Hence, we plan to recruit at least 550 participants to cover both calculations.
SPSS statistical software (Version 26, IBM, SPSS Statistics) was used. Descriptive statistics were performed. For crude bivariate analyses, the Student t-test was used to analyze means with normally distributed data, the Mann-Whitney U test for non-normally distributed data or ordinal data and the Chi-square test (Fisher exact test used if cell size < 5 encountered in ≥ 20% of cells) for categorical data comparing women classified as GBS positive and GBS negative for ano-vaginal colonization. Variables with p < 0.05 on crude bivariate analysis were incorporated into the model for adjusted analysis (multivariable binary logistic regression) to identify independent risk factors of GBS colonization. 2-sided p < 0.05 is taken as the level of significance.
Results
Figure 1 depicts the recruitment flowchart of participants through the study. The first participant was recruited on August 17, 2022, and the last on February 7, 2023. Of 576 eligible women approached to participate, three declined. Five hundred and seventy-three (573) women provided informed written consent and were recruited into the study.
Table 1 shows the 26 selected factors for the entire study population, and then dichotomized and analyzed according to GBS positive and negative status. The p-value from the bivariate analysis of these factors against GBS colonization status were displayed. The bivariate analysis used the appropriate statistical test for the type of data. There were eight variables with p < 0.05 after bivariate analysis; ethnicity, previous neonatal GBS prophylaxis, vaginal discharge in pregnancy, vaginal irritation in pregnancy, antibiotic use in pregnancy (any indication), perineal cleanser after toileting (urination and bowel movement), panty liner use in the preceding two weeks, and sexual intercourse in the past two weeks.
Table 2 presents the eight variables with bivariate p < 0.05 incorporated into the model for multivariable binary logistic regression analysis. This was the a priori model proposed for the study. The crude relative risk (95% confidence interval) and p value after bivariate analysis are shown, as well as the adjusted odds ratio (AOR) and p value following adjustment. After adjustment, six variables were found to be independent risk factors of GBS colonization. In order of their AOR on positive GBS colonization status, from highest AOR, the six significant independent risk factors are previous neonatal GBS prophylaxis AOR 3.18, vaginal irritation in pregnancy AOR 2.69, increasing frequency of sexual intercourse in the preceding two weeks AOR 1.74–2.57, panty liner use in the past two weeks AOR 1.75, Malay ethnicity AOR 1.72, and any antibiotic use in pregnancy AOR 0.47.
Discussion
The prevalence of ano-vaginal GBS colonization in late pregnancy in this study was 41.0%. This is at the upper end of the prevalence range reported in the literature. A study has reported a maternal GBS colonization rate as high as 43.6% [6], contemporary studies report a 37.3% at labor induction [37] and 41.3% rate in women with HIV which was not different from their controls [38].
In our study, after adjustment, the factor with the strongest association for GBS colonization was previous neonatal GBS prophylaxis. Maternal GBS colonization in previous pregnancy has been consistently identified as a risk factor in other studies [16,17,18]. Maternal GBS colonization is a common indication for neonatal GBS antibiotic prophylaxis [4].
Vaginal irritation and itchiness, but not vaginal discharge, was the factor with the next highest odds ratio for GBS colonization in this study. Symptomatic vaginitis has been described in two women heavily colonized with GBS [39]. GBS colonization has also been associated with vulvitis [11]. In non-pregnant women, vaginal GBS colonization is associated vaginal burning/pain but the association is not significant after adjustment for urinary tract, yeast, and herpes simplex virus 2 infections [40].
We found ‘any antibiotic use in pregnancy; to be protective of GBS colonization after adjustment. Our findings corroborate those of a previous study that found the use of antibiotics active against GBS to be associated with a decreased rate of vaginal GBS colonization, but only when the rectum is not also colonized with GBS [40]. In contrast, other studies find that antibiotic exposure in pregnancy is a risk factor for GBS colonization (in univariate analyses but not after adjustment) [26], and also that prenatal antibiotic treatment does not decrease group B streptococcus colonization at delivery [25].
Coitus in the preceding two weeks was also found to be an independent risk factor of GBS colonization with a positive frequency-related trend. In support, in non-pregnant women, recent sexual intercourse increases the risk of vaginal GBS colonization [40] and a doubling in sex acts significantly increased the incidence of some GBS types by 40–80% [21]. In contrast, it has also been reported that sexual behavior does not predict vaginal colonization by GBS [22].
Malay ethnicity in our study cohort was independently predictive of GBS colonization. GBS colonization has been associated with ethnicity or race in several studies [10,11,12]. Recent use of panty liner was also independently predictive of GBS colonization, whilst factors that could precipitate panty liner use such as vaginal discharge in pregnancy were not predictive after adjustment. Vaginal bleeding in pregnancy was not even significant in bivariate analysis in our study.
We have not found within our data as others have for maternal GBS colonization to be associated with age [7, 8], parity [9, 10], body mass index [8, 10, 13,14,15], tobacco use [11, 23, 24], and healthcare worker occupation [35]. Constipation in pregnancy did not contribute to GBS colonization in our findings.
Research implication
Further research focused on building a prediction calculator based on risk factors for GBS colonization at the time of GBS screening is warranted to assist decision making in locations where universal screening remains controversial. Our findings of an association between any antibiotic exposure, the frequency-dependent effect of recent vaginal intercourse, and recent panty liner use should generate interest for further investigation as these factors are plausibly remediable if proven to be causative.
Strengths and limitations
As to strength, our study achieved target sample size of 573 with 235 GBS cases identified, more than adequate for the eight variables in our model for multivariable binary logistic regression. We applied multivariable binary logistic regression to reduce confounding. As to limitations, events were self-reported and subject to recall bias though culture results were not known at questionnaire completion. Our data which was from a single center might reduce generalizability. Using the same swab to sample both sites (anus and vagina) is sanctioned by the Centers for Disease Control and Prevention (CDC) [28] and the American Society for Microbiology [41]. However, it is plausible that culture from a single swab may not be as sensitive for anovaginal colonization as cultures from separate anal and vaginal swabs.
Conclusion
The identification of independent predictors of GBS colonization in late pregnancy may aid in informing the woman and care provider in their shared decision making for microbiological screening at 35–38 weeks gestation in locations where universal GBS screening is not standard of care. Remediable factors of the protective effect of antibiotic exposure in pregnancy and the deleterious effect of recent sexual intercourse and panty liner use warrant further evaluation, not least as potential interventions.
Data availability
The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.
References
Gonçalves BP, et al. Group B streptococcus infection during pregnancy and infancy: estimates of regional and global burden. Lancet Global Health. 2022;10(6):e807–19.
Seale AC, et al. Estimates of the Burden of Group B Streptococcal Disease Worldwide for pregnant women, Stillbirths, and children. Clin Infect Dis. 2017;65(suppl2):S200–19.
Prevention of Group B Streptococcal Early-Onset Disease in newborns. Obstet Gynecol, 2020. 135(2): p. e51–72.
Prevention of early-onset neonatal Group B Streptococcal Disease. BJOG: Int J Obstet Gynecol, 2017. 124(12).
Yücesoy G, et al. Maternal colonisation with group B streptococcus and effectiveness of a culture-based protocol to prevent early-onset neonatal sepsis. Int J Clin Pract. 2004;58(8):735–9.
Gavino M, Wang E. A comparison of a new rapid real-time polymerase chain reaction system to traditional culture in determining group B streptococcus colonization. Am J Obstet Gynecol. 2007;197(4):e3881–4.
Kim EJ, et al. Risk factors for group B streptococcus colonization among pregnant women in Korea. Epidemiol Health. 2011;33:e2011010.
Khalil MR, et al. Maternal age and body mass index as risk factors for rectovaginal colonization with group B Streptococci. Int J Gynecol Obstet. 2022;161(1):303–7.
Akkaneesermsaeng W, et al. Prevalence and risk factors of group BStreptococcuscolonisation in intrapartum women: a cross-sectional study. J Obstet Gynaecol. 2019;39(8):1093–7.
Gopal Rao G, et al. Differential rates of group B streptococcus (GBS) colonisation in pregnant women in a racially diverse area of London, UK: a cross-sectional study. BJOG: Int J Obstet Gynecol. 2019;126(11):1347–53.
Darabi R, et al. The prevalence and risk factors of group B streptococcus colonization in Iranian pregnant women. Electron Physician. 2017;9(5):4399–404.
Valkenburg-van den Berg AW, et al. Prevalence of colonisation with group B streptococci in pregnant women of a multi-ethnic population in the Netherlands. Eur J Obstet Gynecol Reproductive Biology. 2006;124(2):178–83.
Namugongo A, et al. Group B Streptococcus colonization among pregnant women attending Antenatal Care at Tertiary Hospital in Rural Southwestern Uganda. Int J Microbiol. 2016;2016:3816184.
Venkatesh KK, et al. Association between Maternal Obesity and Group B Streptococcus Colonization in a National U.S. Cohort. J Women’s Health. 2020;29(12):1507–12.
Kleweis SM, et al. Maternal obesity and Rectovaginal Group B Streptococcus colonization at term. Infect Dis Obstet Gynecol. 2015;2015:1–5.
Rottenstreich M, et al. The recurrence risk of group B Streptococcus in consecutive deliveries. J Maternal-Fetal Neonatal Med. 2019;33(13):2263–8.
Colicchia LC, et al. Recurrence of group B streptococcus colonization in successive pregnancies. J Perinatol. 2014;35(3):173–6.
Cheng P-J, et al. Risk factors for recurrence of Group B Streptococcus colonization in a subsequent pregnancy. Volume 111. Obstetrics & Gynecology; 2008. pp. 704–9. 3.
Persson K, et al. Several factors influencing the colonization of Group B Streptococci - Rectum probably the Main Reservoir. Scand J Infect Dis. 1981;13(3):171–5.
Collins TS, et al. Group B streptococcal colonization in a developing country: its association with sexually transmitted disease and socioeconomic factors. Am J Trop Med Hyg. 1998;59(4):633–6.
Foxman B, et al. Risk factors for group B streptococcal colonization: potential for different transmission systems by capsular type. Ann Epidemiol. 2007;17(11):854–62.
Newton ER, Butler MC, Shain RN. Sexual behavior and vaginal colonization by group B streptococcus among minority women. Obstet Gynecol. 1996;88(4 Pt 1):577–82.
Spradley FT, et al. Group B streptococcal colonization: prevalence and impact of smoking in women delivering term or near term neonates in a large tertiary care hospital in the southern United States. PLoS ONE. 2020;15(9):e0239294.
Terry RR, et al. Risk factors for maternal colonization with group B beta-hemolytic streptococci. J Osteopath Med. 1999;99(11):571–571.
Baecher L, Grobman W. Prenatal antibiotic treatment does not decrease group B streptococcus colonization at delivery. Int J Gynaecol Obstet. 2008;101(2):125–8.
Capraro GA, et al. Association of sexually-transmitted infection and African–American race with Streptococcus agalactiae colonization in pregnancy. Volume 9. Antimicrobial Resistance & Infection Control; 2020. 1.
Regan JA, Klebanoff MA, Nugent RP. The epidemiology of group B streptococcal colonization in pregnancy. Vaginal infections and Prematurity Study Group. Obstet Gynecol. 1991;77(4):604–10.
Verani JR, McGee L, Schrag SJ. Prevention of perinatal group B streptococcal disease–revised guidelines from CDC, 2010. MMWR Recomm Rep. 2010;59(Rr–10):1–36.
Baltimore RS. Consequences of prophylaxis for group B streptococcal infections of the neonate. Semin Perinatol. 2007;31(1):33–8.
Prevention of early-onset neonatal Group B Streptococcal Disease: Green-top Guideline 36. BJOG, 2017. 124(12): p. e280–305.
Paul SP et al. NICE guideline review: neonatal infection: antibiotics for prevention and treatment (NG195) Archives of disease in childhood - Education & practice edition, 2021: p. edpract-2021-322349.
Raj M, Razali N, Sulaiman S. Screening of Antenatal Mothers and Prevention of Perinatal Group B streptococcal infection. J Univ Malaya Med Centre (JUMMEC). 2009;12(1):27–30.
Bey M, Pastorek JG 2nd, and, Miller JM Jr. Group B streptococcal colonization in the diabetic gravida patient. Am J Perinatol. 1992;9(5–6):425–7.
Farideh A, Abdolkarim H, Naderi Nasab M. Comparison of Group B Streptococcal colonization in the pregnant Diabetic and non-diabetic women. Acta Medica Iranica, 1970. 47(2).
Stapleton RD, et al. Risk factors for group B streptococcal genitourinary tract colonization in pregnant women. Obstet Gynecol. 2005;106(6):1246–52.
Drossman DA, Hasler WL. Rome IV-Functional GI disorders: disorders of Gut-Brain Interaction. Gastroenterology. 2016;150(6):1257–61.
McCoy JA, et al. Association between intrapartum antibiotic prophylaxis for Group B Streptococcus colonization and clinical chorioamnionitis among patients undergoing induction of labor at term. Am J Obstet Gynecol. 2023;229(6):e6721–8.
Morgan JA, et al. Group B Streptococcus Rectovaginal colonization and resistance patterns in HIV-Positive compared to HIV-Negative pregnant patients. Am J Perinatol. 2021;40(14):1573–8.
Honig E, Mouton JW, van der Meijden WI. Can group B streptococci cause symptomatic vaginitis? Infect Dis Obstet Gynecol. 1999;7(4):206–9.
Meyn LA, Krohn MA, Hillier SL. Rectal colonization by group B Streptococcus as a predictor of vaginal colonization. Am J Obstet Gynecol. 2009;201(1):e761–7.
Filkins L et al. American Society for Microbiology Provides 2020 Guidelines for Detection and identification of Group B Streptococcus. J Clin Microbiol, 2020. 59(1).
Acknowledgements
The authors are indebted and thankful to the women who participated in this study and to the Department of Obstetrics and Gynecology for internally funding the study.
Funding
This research was internally funded by the Department of Obstetrics and Gynecology, University Malaya.
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All authors (RE, BKL, MH, FG and PCT) contributed to elements of the study. PCT and RE conceptualized the study, RE recruited participants, and collected and cleaned the data. RE did the primary data analysis assisted by PCT. All authors contributed to data interpretation. PCT and RE co-wrote the manuscript draft assisted by FG; BKL and MH provided critique to refine the manuscript. All authors assert ownership over and responsibility for the manuscript.
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This study was approved by the Medical Ethics Committee of University Malaya Medical Centre (UMMC) on August 9, 2022, reference number 2022328-11120. Written informed consent was obtained from the participants.
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This study was conducted at University Malaya Medical Centre, Kuala Lumpur, Malaysia.
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Esmaon, R., Lim, B., Gan, F. et al. Sexual activity, vaginal symptoms, maternal perineal hygiene behavior, and constipation on ano-vaginal colonization of group B streptococcus in near term pregnancy. BMC Pregnancy Childbirth 24, 461 (2024). https://doi.org/10.1186/s12884-024-06616-7
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DOI: https://doi.org/10.1186/s12884-024-06616-7