Table 3.

Estimates and 95% confidence intervals for the mean infant birthweight for maternal and paternal body mass indexes.

Maternal BMI (kg/m2)	Paternal BMI (kg/m2)	M1: birthweight (g) [95% CI]	M2: birthweight (g) [95% CI]	M3: birthweight (g) [95% CI]
20	20	3191 [3112, 3270]	3176 [3095, 3256]	3176 [3066, 3286]
35	20	3481 [3382, 3580]	3457 [3354, 3560]	3427 [3287, 3567]
20	35	3335 [3250, 3421]	3309 [3215, 3403]	3296 [3196, 3395]
35	35	3427 [3355, 3500]	3412 [3336, 3487]	3422 [3344, 3499]

Note: BMI = body mass index. Model M1 extends M0 with the inclusion of the pairwise linear interaction of parental BMIs. Model M2 extends M1 with the inclusion of nonlinear terms for maternal BMI. Model M3 is the full model with both nonlinear terms for both parental BMIs and their pairwise linear interaction. The following adjustment factors were included in the models: gestational age, parental age, Socio-Economic Indexes for Areas score, year of delivery, and delivery method.