Table 1.
Characteristics of the covariates.
| Covariates | Definitions and Categories |
|---|---|
| Maternal age | Maternal age was taken from medical reports. This variable was defined as completed maternal age at conception; in years. Maternal age as a continuous variable was a covariate. |
| Pre-pregnancy BMI (body mass index) |
Pre-pregnancy BMI was self-reported in the Questionnaire This variable was defined as the quotient of pre-pregnancy weight (kg) and height (meters) squared. BMI as a continuous variable was a covariate. BMI was assessed in the five following categories as subgroups: (1) normal BMI (18.5–24.9); (2) underweight (<18.5); (3) overweight (25.0–29.9); (4) obesity (≥30); and (5) BMI ≥ 25 kg/m2. |
| GWG (gestational weight gain) |
GWG was based on maternal weight before childbirth (from medical reports) and pre-pregnancy weight (self-reported). This variable was defined as the difference between the maternal weight before childbirth and the weight before pregnancy. GWG was assessed in the three following categories regardless of pre-pregnancy BMI categories (according to the Institute of Medicine (IOM) recommendations from 2009): (1) GWG in the range; (2) GWG above the range; and (3) GWG below the range. GWG out of the range was a covariate. |
| Multiparity | Parity was taken from medical records. The two following categories of parity were taken into consideration: (1) multiparity (≥1 prior childbirths) and (2) primiparity (zero prior childbirth). Multiparity was a covariate. |
| Smoking | Smoking status was self-reported in the Questionnaire. Smoking was assessed in the three following categories as subgroups: (1) women who had never smoked; (2) women who smoked before pregnancy); and (3) women who smoked in the first trimester. The category of ‘smokers in the first trimester’ was a covariate. |
| Prior GDM | The maternal history was taken from medical reports. This variable was defined as gestational diabetes mellitus (GDM) in previous pregnancies. The two following categories were taken into consideration: (1) prior GDM; (2) no prior GDM. Prior GDM was a covariate. |
GDM: gestational diabetes mellitus.