Background: Maternal colonization with Group B Streptococcus (GBS) is linked to adverse pregnancy events such as preterm births, prelabor rupture of membranes, and neonatal sepsis. Isolating the organism during antenatal care can enable early treatment and mitigate adverse outcomes.
Objective: This study aimed to determine the prevalence and outcome of GBS colonization in pregnancy.
Methodology: A prospective cohort study involved 333 pregnant women at the maternity unit of Irrua Specialist Teaching Hospital (ISTH). Vaginal and rectal swabs were obtained at 28 weeks of gestation and above during antenatal care or labor, and babies were sampled after delivery. Mothers and babies were followed up until six weeks post-delivery for GBS complications. Continuous variables were summarized using mean, median, and standard deviation, while categorical variables were summarized using proportions. A p-value of less than 0.05 was considered statistically significant.
Results: Among the 333 women, 32 were positive for GBS, giving a prevalence of 9.6%. None of the neonates delivered to these women were positive for GBS. Complications among GBS-positive women included urinary tract infection (25%), preterm labor (25%), prelabor rupture of membranes (21.9%), preterm delivery (21.9%), and febrile illness (18.8%). The mean age of the women was 30.0 years (±5.3), and increased parity was significantly associated (P = 0.01). A few neonates experienced complications not attributed to GBS colonization.
Conclusion: The prevalence of GBS in pregnancy at ISTH is 9.6%. Although GBS infection can be harmful, this study did not show significant complications. There was no mother-to-child transmission of GBS.

Group B streptococcus, Maternal outcomes, Neonatal morbidities, Adverse pregnancy outcomes, Group B streptococcus colonization.

The Lancefield group B Streptococcus (GBS), also known as Streptococcus agalactiae, is a β-hemolytic gram-positive coccus.[1] It is a bowel commensal, colonizing the female genital tract in approximately 20% of women and is estimated to colonize the vagina in 10-35% of pregnant women.[2] During pregnancy, GBS is typically harboured asymptomatically in mucous membranes, including genital, rectal, and pharyngeal mucosa. It is known to cause urinary tract infections (UTI) in pregnancy and has been implicated in preterm labor, prelabor rupture of membranes (PROM), postpartum endometritis, and neonatal sepsis. GBS can be a significant cause of morbidity and mortality among neonates, infants, the elderly, and immunosuppressed individuals.[3] It is recognized as the most common organism responsible for early-onset neonatal sepsis. Neonatal sepsis can manifest as early-onset disease (EOD), occurring within six days of birth, or late-onset disease (LOD), occurring seven days or more after birth.[4] Although there are various serotypes of GBS due to their capsular polysaccharides, they are not evenly distributed globally.[5,6]

GBS colonization is now commonly reported as a cause of adverse pregnancy events in both developing and developed regions. However, the true burden in many settings in developing countries and the implications during pregnancy remain to be fully determined.[7,8] Treatment guidelines for screening and antibiotic prophylaxis are being formulated but remain unclear in our setting.[4,9] More evidence and information are needed to create comprehensive guidelines. This study aimed to determine the prevalence and maternal and neonatal outcomes of GBS colonization in pregnancy. Findings from this study are intended to generate data on the burden of the disease as well as to provide valuable recommendations and potential policy changes in the management of pregnant women with GBS.

This study employed systematic sampling to enrol 333 pregnant women into the study. Participants were selected from the labour ward and antenatal care (ANC) via the attending nurse’s station. The first participant from each frame was selected using random sampling, and every 6th individual was added systematically. A structured questionnaire was used to collect information from eligible participants after pretesting. The questionnaire collected socio-demographic characteristics, obstetric history, and information on the current pregnancy. Vaginal and anal swabs were obtained from participants without the use of speculum or prior cleaning with an antiseptic.[10-12] The swab was transported to the microbiology laboratory and frozen at -20°C prior to polymerase chain reaction (PCR) studies. The PCR reaction was conducted using the Solis Biodyne 5X FIREPol Master mix. Thermal cycling was conducted in a Techne Prime thermal cycler. Data was analysed using International Business Machines (IBM) SPSS Software version 27.0. The chi-square test was used to test the association between maternal GBS colonization and pregnancy outcomes.

Ethical considerations: Approval was sought from ISTH’s health research ethics committee (HREC) before the commencement of the study. Written informed consent was obtained from pregnant women, and confidentiality was maintained by use of study code numbers.

Over the 6-month study period, 432 pregnant women were assessed for enrolment. After counselling, 350 provided informed consent, while 80 declined or did not meet the inclusion criteria. Of the 350 consenting participants, 17 did not plan to receive follow-up care at ISTH and were excluded from the study, leaving 333 participants. The participants’ ages ranged from 18 to 45 years, with a mean age of 30.3 years (±5.2). The majority (46.85%) were between 31 and 40 years old. Notably, the mean age of GBS-positive participants (32.2±4.5) was significantly higher than that of GBS-negative participants (30.0±5.3) (P=0.03). In terms of education, the majority of the participants in both groups had post-primary education (GBS-positive: 96.9%, GBS-negative: 98.3%). No significant differences were found between the marital status and occupational status of participants with positive or negative GBS colonization.

Table 1: Sociodemographic characteristics of respondents (*=p<0.05)

Table 1 represents the sociodemographic characteristics of 333 pregnant women, including 32 GBS-positive and 301 GBS-negative participants.

• The mean age of GBS-positive participants was significantly lower than that of GBS-negative participants (30.0 ± 5.3 vs. 32.2 ± 4.5, p=0.03).
• The majority of the participants were married (95.2%) and had secondary or tertiary education (98.2%).
• There was no significant difference in occupational status between GBS-positive and GBS-negative participants.

Table 2: Sociodemographic and obstetric characteristics with predisposing risk factors of GBS mothers attending ANC

Table 2 represents the sociodemographic and obstetric characteristics of 333 pregnant women attending ANC, including 32 GBS-positive and 301 GBS-negative participants. The results show:

• Women with secondary and tertiary education had lower odds of GBS colonization (OR 0.9 and 0.1, respectively).
• Multiparity was associated with increased odds of GBS colonization (OR 3.7).
• Frequent sexual intercourse, multiple sexual partners, and diabetes mellitus in pregnancy were identified as risk factors for GBS colonization (OR 6.0, 9.9, and 6.1, respectively).

Table 3: Maternal outcome and anticipated complications

Table 3 represents the maternal outcomes and anticipated complications of 333 pregnant women, including 32 GBS-positive and 301 GBS-negative participants. The results show:

• GBS colonization was associated with increased odds of urinary tract infection (OR 6.8), premature rupture of membranes (OR 2.6), febrile illness (OR 8.5), preterm labor (OR 6.4), and preterm delivery (OR 2.7).
• No significant difference was found in the type of delivery between GBS-positive and GBS-negative participants.
• Postpartum endometritis was less likely to occur in GBS-positive women, but this finding was not statistically significant.

This study investigated the maternal and neonatal outcomes of Group B Streptococcus (GBS) colonization in pregnant women at ISTH Irrua. The prevalence of GBS colonization was 9.6%, which is comparable to previous studies in Nigeria.13 In this study, GBS colonization was associated with increased risk of UTIs, PROM, febrile illness, preterm labor, and preterm delivery. There are risk factors involved in predisposing a pregnant patient to become GBS colonized and of the 333 participants, none were previously confirmed to have had GBS colonization because they have never carried out any test on GBS, though some of the participant had other risk factors for GBS such as frequent sexual intercourse (12.5%), DM in pregnancy (9.4%), and multiple sexual partners (6.3%). In this study, a positive GBS carriage was 1.1 times likely to occur in the unbooked participants than in booked patients, although there was no statistical significance (p = 0.83). Frequent sexual intercourse increased the risk of GBS colonization by 6 times (OR 6.0, CI 1.7 – 21.8, p = 0.01), and multiple sexual partners by 9.9 times (OR 9.9, CI 1.3 – 73.3, p = 0.02). Another risk factor was DM in pregnancy, which increased the risk of GBS colonization by 6.1 (OR 6.1, CI 1.4 – 26.9, p = 0.02). They were all statistically significant. None of the participants in the study smoked cigarettes. Using grandmultipara as reference, a positive GBS was 90% less likely among a primigravida (p = 0.01) while it was 3.7 times more likely to occur among multipara, this was statistically significant (p = 0.01) with the GBS status and thus with increase in parity there is an increase in positive GBS status. Multiparas had the highest proportion of GBS colonization (62.5%), followed by primipara (15.6%), while the lowest proportion of women with GBS was primigravida (6.3%). This is as compared to the previous study, which had a similar finding of more GBS colonization among multiparous women.[13]

Although there are several complications that may result from GBS colonization in pregnancy, it was noticed from this study that of the 32 patients with GBS colonization had either one or a combination of the following GBS complications: urinary tract infection (25.0%) following urine MCS testing, febrile illness (18.8%), PROM (21.9%), however, they were not severe enough to cause severe maternal morbidity and they were all statistically significant. Other complications noticed among GBS-positive carriers were preterm labour (25.0%) and preterm delivery (21.9%), but no positive GBS participant had stillbirth or postpartum endometritis. These complications were only seen among the GBS negative participants, i.e., stillbirth (0.9%) and postpartum endometritis (0.3%); however, they were not statistically significant.

In pregnant individuals, GBS is a known source of asymptomatic bacteriuria, urinary tract infection (UTI), and pyelonephritis, 14, and in this study, UTI complicated 25% of the pregnancies that were confirmed GBS positive.[14] This is less than the study by Clouse et al, 3 that noticed 53.3% of GBS positive patients had UTI; however, Edwards et al, 15 noticed a far reduced percentage of 1.6. However, this may be due to the reduced number of GBS colonized people that were studied. PROM complicated 21.9% of those who were positive for GBS, which is in keeping with several studies that have reported significantly higher rates of preterm labour, PPROM, and preterm birth in GBS colonized pregnant women.[15,16] In contrast, Kim et al, reported no statistically significant association between vaginal GBS colonization and preterm labour or PPROM. A recent systematic review reported no significant association between GBS colonization in pregnant women and preterm labor. This issue remains controversial, and there is currently no consensus regarding the effect of GBS colonization on preterm labour and PPROM.[17]

Risk factors for GBS colonization included frequent sexual intercourse, multiple sexual partners, and DM in pregnancy. Most participants (46.8%) were between 31 and 40 years old, and the mean age was 30.3 years. Participants with secondary and tertiary education had lower odds of GBS colonization. The study’s findings suggest that targeted GBS screening may be

beneficial for pregnant women with risk factors. However, the study’s limitations include a single-centre design, a limited sample size, and potential recall bias.

Recommendation: Maternal GBS screening may be considered for pregnant women with risk factors. Guidelines on prevention and management should be advocated in antenatal clinics.

GBS colonization is a significant risk factor for adverse pregnancy outcomes. Targeted screening and prevention strategies may be effective in reducing the risk of GBS-related complications. Further studies are needed to confirm these findings and inform guidelines for GBS screening and management in Nigeria.

Not reported

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Corresponding Author:
Joseph Okoeguale
Department of Obstetrics and Gynaecology
Ambrose Alli University, Ekpoma, Nigeria
Institute of Viral and Emergent Pathogens, Irrua Specialist Teaching Hospital, Nigeria
Email: okoegualejoseph85@gmail.com

Co-Authors:
Enodiana Xavier (Lead Author), Ikheloa Joseph, Eigbefoh Joseph, Afolabi Happy
Department of Obstetrics and Gynaecology
College of Medicine, Ambrose Alli University, Ekpoma, Nigeria

Samuel Olowo
Department of Medical Microbiology
Ambrose Alli University, Ekpoma, Nigeria

Xavier Enodiana, Joseph Ikheloa, Joseph Okoeguale, and Olowo Samuel led the study’s conceptualization. Joseph Eigbefoh, Anthonia Njoku, Happy Afolabi, Joseph Ikheloa, and Joseph Okoeguale managed data curation, while methodology was developed by Enodiana, Njoku, Afolabi, Ikheloa, and Okoeguale. Project administration was overseen by Okoeguale and Eigbefoh. Resources were provided by Samuel, Njoku, Afolabi, Ikheloa, and Okoeguale. Software tasks were handled by Njoku and Ikheloa. Supervision was conducted by Enodiana, Ikheloa, and Okoeguale. Writing – review and editing were performed by Enodiana, Njoku, Afolabi, Ikheloa, Okoeguale, and Samuel.

Approval was sought from ISTH’s HREC before the commencement of the study. Written informed consent was obtained from pregnant women, and confidentiality was maintained by use of study code numbers.

The authors declare no conflicts of interest.

None

https://doi.org/10.63096/medtigo3062331

Xavier E, Okoeguale J, Joseph I, et al. Maternal Outcome of Group B Streptococci Colonization in Pregnant Women: A Hospital Based Study at Irrua Specialist Teaching Hospital, Edo State, Nigeria. medtigo J Med. 2025;3(3):e3062331. doi:10.63096/medtigo3062331 Crossref