Data Analyses
A total sample of 803 mother newborn dyad was recruited in the study.
The outcome variable of interest was GBS colonization among pregnant
women delivering term or near term infants 35+ weeks gestational age.
The primary independent variable of interest was active tobacco smoking
throughout pregnancy as determined by the number of cigarettes smoked
per day. In the univariate analysis, tobacco smoking was categorized as
0 cigarette/day, 1 cigarette/day, 2 cigarettes/day, and 3 +
cigarettes/day respectively for trend analysis. Test of trend was also
explored for maternal age. Initially maternal age was empirically
categorized into 2 groups (< 20 year of years versus 20+
years). A trend analysis for this variable was then conducted to
determine whether GBS rates varied by the various maternal age groups.
When a clear trend emerged, maternal age was subsequently empirically
expanded to 5 groups (<20, 20-24, 25-29, 30-34, and 35+) to
explore whether the trend continued. Tests of trends were also explored
for the other independent variables of interest (birthweight,
gestational age) but were not significant so these variables were left
dichotomized in the univariate analysis. In the multiple logistic
regression analyses, all the independent variables of interest were left
dichotomized for simplicity of analyses.
Descriptive statistics were conducted. Univariate analysis was conducted
to determine if each of the selected variables was associated with
maternal GBS colonization using the X2 analysis of
comparisons of proportions with Fischer’s exact test. Next, a multiple
logistic regression analysis was conducted using only the significant
variables in the univariate analysis to determine if each of these
factors was still predictive of maternal GBS colonization after
controlling for the other potential confounders. The SPSS statistical
software (IBM, Armonk, NY 2018) was used in the analyses. A p value of
<0.05 was used as test of significance in all cases.