Table 2 shows the relative risks of maternal outcomes by single
and joint effects of maternal prepregnancy BMI and GWG.
Numbers of subjects of maternal outcomes by joint effects of
maternal prepregnancy BMI and weight gain during pregnancy
are presented in Table S1. After adjustment for all confounding
factors, maternal prepregnancy BMI was positively associated with
risks of GDM, pregnancy-induced hypertension, caesarean delivery,
and preterm delivery. Maternal excessive GWG was
associated with increased risks of pregnancy-induced hypertension
and caesarean delivery, and a decreased risk of preterm delivery,
and maternal inadequate GWG was associated with an increased
risk of preterm delivery, compared with maternal adequate GWG.
In the joint analyses of maternal prepregnancy BMI and GWG
with maternal outcomes, the positive associations of prepregnancy
BMI with the risks of GDM, pregnancy-induced hypertension,
caesarean delivery, and preterm delivery were consistent in
subjects with different levels of GWG. Women with both
prepregnancy obesity and excessive GWG or adequate GWG
had the highest (2.2–7.1 folds) risks of GDM, pregnancy-induced
hypertension, and caesarean delivery compared with women with
normal prepregnancy BMI and adequate GWG