TABLE 3.

Adjusted association between kilogram gain in maternal weight and mean birth weight among dichorionic twin pregnancies, National Institute of Child Health and Human Development Fetal Growth Studies – Twins (2012–2013)¹

Maternal weight gain2	Birth weight, g (95% CI)
0–13 wk (n = 141)	15.4 (−1.7, 32.6)
14–20 wk (n = 139)	132.8 (56.6, 208.9)*
21–27 wk (n = 131)	57.0 (2.7, 111.3)*
28–34 wk (n = 99)	14.3 (−37.6, 66.2)

¹Models adjusted for maternal age (19–24, 25–29, 30–34, 35–39, and ≥40 y), race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, or Asian), prepregnancy BMI, height, nulliparity, married status, education (less than high school, high school diploma, general equivalency diploma or equivalent, some college or associate degree, Bachelor’s degree, Master’s degree, or advanced degree), employed or full-time student status, smoking (no, before pregnancy, or during pregnancy), fertility intervention, chronic hypertension, fetal sex (male/male, female/female, male/female, or unknown/unknown), gestational age at delivery, and, where applicable, gestational weight gain in the previous time period. Estimates are based on linear regression models. ^*Indicates estimates that are significant (P < 0.05).

²Sample size decreases due to early deliveries.