Table 5.
Linear regression models of newborn weight and length by GWG pattern by trimester1
| Birth weight, g n=156 |
Birth length, cm n=137 |
||||||
|---|---|---|---|---|---|---|---|
| Coef. | 95% Confidence Interval |
p-value | Coef. | 95% Confidence Interval |
p-value | ||
| Weight gain2, kg | |||||||
| Prepregnancy BMI | 8.5 | (−16.4, 33.4) | 0.50 | 0.03 | (−0.02, 0.07) | 0.21 | |
| Trimester 1 Medium | −291.2 | (−1235.8, 653.4) | 0.54 | 0.42 | (−0.08, 0.92) | 0.10 | |
| Trimester 1 High | −615.6 | (−16.07.1, 375.9) | 0.22 | 0.49 | (−0.05, 1.02) | 0.08 | |
| Trimester 2 Medium | 461.4 | (−370.9, 1293.7) | 0.28 | 0.27 | (−0.22, 0.77) | 0.27 | |
| Trimester 2 High | 1437.1 | (267.9, 2606.4) | 0.02 | 0.82 | (0.21, 1.43) | 0.01 | |
| Trimester 3 Medium | 242.6 | (−573.4, 1058.5) | 0.56 | −0.16 | (−0.63, 0.31) | 0.50 | |
| Trimester 3 High | −383.2 | (−1536.7, 770.3) | 0.51 | 0.08 | (−0.57, 0.73) | 0.81 | |
| Trimester 1 Medium*Prepregnancy BMI | 15.4 | (−22.6, 53.4) | 0.43 | - | |||
| Trimester 1 High*Prepregnancy BMI | 28.7 | (−9.7, 67.1) | 0.14 | - | |||
| Trimester 2 Medium*Prepregnancy BMI | −15.3 | (−48.1, 17.5) | 0.36 | - | |||
| Trimester 2 High*Prepregnancy BMI | −42.6 | (−89.3, 4.0) | 0.07 | - | |||
| Trimester 3 Medium*Prepregnancy BMI | −12.2 | (−44.9, 20.5) | 0.46 | - | |||
| Trimester 3 High*Prepregnancy BMI | 10.0 | (−36.1, 56.0) | 0.67 | - | |||
| Rate of weight gain, kg/wk | |||||||
| Prepregnancy BMI | −0.5 | (−14.5, 13.5) | 0.94 | 0.02 | (−0.02, 0.06) | 0.29 | |
| Trimester 1 Medium | −84.8 | (−248.0, 78.3) | 0.31 | −0.12 | (−0.60, 0.36) | 0.63 | |
| Trimester 1 High | 33.8 | (−130.7, 198.2) | 0.69 | 0.22 | (−0.26, 0.69) | 0.37 | |
| Trimester 2 Medium | 29.1 | (−138.6, 196.8) | 0.73 | 0.39 | (−0.10, 0.89) | 0.12 | |
| Trimester 2 High | 355.9 | (182.1, 529.7) | <0.001 | 0.85 | (0.33, 1.38) | 0.002 | |
| Trimester 3 Medium | −113.6 | (−270.4, 43.2) | 0.15 | −0.17 | (−0.63, 0.29) | 0.47 | |
| Trimester 3 High | −83.6 | (−259.1, 91.8) | 0.35 | −0.23 | (−0.74, 0.29) | 0.38 | |
Low tertile of gestational weight gain is reference for each trimester. Adjusted for gestational age at delivery, maternal education, race/ethnicity, age, parity and infant sex.
An interaction term between prepregnancy BMI and total weight gain pattern is included in the model with infant birth weight outcomes; thus, individual effect estimates cannot be interpreted without accounting for prepregnancy BMI. For illustration, predicted infant birth weight was increased by 823 g (p=0.01), 755 g (p=0.02), and 687 g (p=0.03) for women with a prepregnancy BMI of 18, 20 and 23 kg/m2, respectively; these estimates are based on linear combinations of the beta coefficients for n BMI (e.g., prepregnancy BMI β *n + Trimester 2 High β + Trimester 2 High β*Prepregnancy BMI β*n). For women with higher prepregnancy BMI (≥24 kg/m2), the pattern of weight gain was not associated with infant birth weight (all p>0.05).
BMI, body mass index; GWG, gestational weight gain; TBW, total body water.