Statistical Methods
Data were expressed as mean (standard deviation) for continuous
variables and n (%) for categorical variables. Students t-test and
χ2-square test or Fisher’s exact test, were used for comparing outcome
groups for continuous and categorical data, respectively.
Univariable logistic regression analysis was performed to examine the
association between racial origin and PE and GH using white racial
origin as the reference. Multiple logistic regression analysis with
manual backward elimination was performed for modelling total PE,
preterm PE with delivery at <37 weeks of gestation, early PE
with delivery at <34 weeks and total GH using racial origin,
maternal age, weight, height, mode of conception, smoking, history of
chronic hypertension, diabetes mellitus, APS or SLE, history of PE in a
previous pregnancy or family history of PE. Before performing the
multiple regression analysis, continuous variables were centered by
subtracting the median from each measured value (67 from maternal weight
in kg, 1.65 from maternal height in meters and 30 from maternal age in
years).
The statistical software R was used for data
analyses.29