Prevalence of the Bacterial Vaginosis and Group B Streptococcus in Term and Pre-term Pregnancies

Abstract

Background and objective:
Several studies have been conducted about Bacterial Vaginosis and its relation with preterm labor that was accompanied with controversial results. The aim of this study was to compare the frequency of Bacterial Vaginosis and common genitourinary infections between term and pre-term pregnancies.

Methods:
In a case-control study, 249 pregnant women admitted to Shohadyae Tajrish Hospital in 2004-2006 were studied. The cases (n=125) were chosen from pregnant women with pre-term labor and the controls (n=124) were chosen from women who had term labor.

All the patients underwent Bacterial Vaginosis investigation (Amsel criteria) and group B streptococcus, Trichomonas, Candida Albicans and E.coli with smear and culture (from cervix).

Results:
Bacterial Vaginosis was significantly higher in patients with rupture of membranes compared with patients with intact membranes (64.29% vs. 35.71%). The means of age, number of pregnancies, deliveries, living children, history of abortion, infection with B streptococcus, Trichomonas, Gardnerella vaginalis, and Candida Albicans showed no significant difference between two groups and only infection with E.coli in the pre-term group was significantly higher (11.20% vs. 1.61%). Also history of preterm labor (16.98% vs. 6.42%) and rupture of membranes (40% vs. 12.38%) was significantly higher in preterm group.

Conclusions:
No significant relation was found between Bacterial Vaginosis and preterm labor, only infection with E.coli was significantly higher in the pre-term group in comparison with term pregnancies.

Introduction
There are several factors which predispose to preterm delivery. It seems that activation of hypothalamus-pituitary-adrenal axis of mother or the fetus, decidual hemorrhage, pathologic uterine distension and infection are influencing factors (1). Epidemiologic studies have shown that stress and infection of maternal genitourinary system independently and significantly increase the risk of preterm labor (2).

Theoretically, pathogenic organisms ascend via lower genital organs to uterine and may cause fetal membrane inflammation which leads to preterm rupture of membranes and labor (3). Maternal genitourinary infection can initiate the process of labor and cause preterm labor via different mechanisms including activation of cytokine cycle and acceleration of labor process. Vaginal infection or colonization increases the risk of fetal membrane infection and inflammatory cytokines affect the process of labor (4). Different studies have suggested a wide range of microorganisms including group B streptococcus, Trichomonas, Nisceria Gonorrhea, E.coli, Bacterial Vaginosis, and Candida Albicans as the predisposing factors of preterm labor (5-7). Various studies about Bacterial Vaginosis have ended up in controversial results. There have been several studies showing a significant relationship between Bacterial Vaginosis and preterm labor (8-13) while some other studies have denied this relationship (14-18) and even some of them have indicated a reverse relationship (19, 20). Moreover, the prevalence of Bacterial Vaginosis are widely different in vaginal smears of asymptomatic women in different countries (21). Therefore, the prevalence of Bacterial Vaginosis and its relationship with preterm labor has to be separately investigated in each nation (14).

The purpose of this study was to evaluate the prevalence of Bacterial Vaginosis and other common vaginal infections in pregnant women with term or preterm labor in Shohada Tajrish Hospital from 2005 to 2007. Our study included 249 patients in two groups of term (124 patients) and preterm (125 patients) labor.

Materials & Methods
We enrolled 249 patients who referred to Shohada Tajrish Hospital from 2005 to 2007 for delivery in a case-control study after approval of ethics committee of Research Deputy of Shahid Beheshti University of Medical Sciences. The cases included 125 women who experienced preterm labor and the controls were 124 women with term delivery.

After obtaining the data related to demographic variables by a questionnaire, the patients underwent microbiological studies to evaluate infection or colonization with Bacterial Vaginosis (KOH smear and wet smear for clue cells and PH evaluation by Amsel method), Group B Streptococcus (Blood Agar media), Trichomonas (vaginal wet smear), Candida Albicans (visualizing hyphae after adding KOH to simple smear) and E.Coli (EMB media). The smear and culture samples were taken from the cervix with a sterilized swab prior to the first vaginal examination by the chief resident or the senior residents in charge in the primary visit. The samples of the cultures were taken immediately to the laboratory of the hospital to be cultured in the mentioned media. The smears were all reported by the chief resident and the results of the cultures were confirmed by the Pathology Department of the hospital.

The data was analyzed by t-test, chi-square or Fischer’s exact test in SPSS ver. 12.0. P values below 0.05 were assumed significant.

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