Prevalence of GBS Colonization by Sociodemographic
Characteristics
Among the 803 pregnant included in the study, GBS status of 67 women was
unknown and when these were excluded from the analysis, the valid
prevalence of GBS was 36%. However, when these missing cases were
include, the overall prevalence rate of GBS colonization dropped
slightly to 32%. GBS carriage was least prevalent among the none
smokers (32%) but rose sharply to 53 % if the subjects smoked 1
cigarette/day and the rate almost doubled to 63% if the subjects smoked
2+cigarettes/day (p of trend=0.003). When maternal age was categorized
into 2 groups (teens vs older), GBS was higher among the teen mothers
(<20 years) as compared to their older counterparts (20+
years, P=0.006; also see Table 2). Furthermore, when maternal age was
categorized into 5 groups, the prevalence of GBS was highest among women
<20 years (49%), dropped to 40% in women 20-24 years, and
30% in women 25 to 29years. However, there was a small spike to 36 %
in women 30-35 years but the rate dropped again to 28% in women 35 +
years. In general, therefore, there was a decreasing trend of GBS
colonization with increasing maternal age (P of Trend=0.023; also see
Figure 1). Interestingly, this trend was only true among non-smokers.
Among the smokers, however, there was no downward trend of maternal in
GBS colonization by maternal age (P of Trend=0.935; also see Figure 2).
The prevalence of GBS colonization was higher among preterm birth
infants (<37 weeks gestational age) as compared to their term
birth counterparts (37 weeks +; P=0.041). Mothers of low birth weight
infants were (<2500 grams) were more likely to be colonized by
GBS (55.2%) than mothers with heavier or normal birth weight babies
(2500+ grams; 34.2%, P=0.02).
GBS colonization varied widely among the racial groups and was lowest
among Asian /Pacific Island Americans (22%) as compared to the Latinos
(26%), White Americans (31%) or African American (49%, P
<0.001). Furthermore, the proportion of colonization was more
prevalent among women with any history of substance use (54%) as
compared to those without any use (35%; P=0.004). Thus, of the nine
variables explored in this study, only 3 viz. gestational diabetes
mellitus, parity, and gender were not predictive of GBS carriage (also
see Table 2).