TABLE 2.
Adjusted association between each kilogram gain in maternal weight and subsequent fetal size the following week among dichorionic twin pregnancies, National Institute of Child Health and Human Development Fetal Growth Studies – Twins (2012–2013)1
| Fetal growth outcome the following week |
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| Maternal weight gain exposure2 | EFW, g (95% CI) | AC, mm (95% CI) | BPD, mm (95% CI) | HC, mm (95% CI) | FL, mm (95% CI) | HL, mm (95% CI) | HC:AC ratio (95% CI) |
| 0–13 wk (n = 143) | 0.1 (−0.4, 0.6)3 | 0.0 (−0.3, 0.3) | 0.0 (−0.1, 0.1) | 0.0 (−0.3, 0.3) | 0.1 (0.0, 0.1) | 0.0 (−0.1, 0.1) | −0.001 (−0.005, 0.003) |
| 14–20 wk (n = 141) | 10.5 (1.2, 19.8)* | 2.3 (0.5, 4.1)* | 0.6 (0.1, 1.1)* | 1.5 (−0.1, 3.2) | 0.2 (−0.2, 0.7) | 0.4 (−0.1, 0.8) | −0.007 (−0.014, 0.000) |
| 21–27 wk (n = 132) | 21.3 (0.6, 42.0)* | 1.7 (−0.1, 3.5) | 0.2 (−0.3, 0.6) | 0.7 (−0.6, 2.0) | 0.3 (0.0, 0.6)* | 0.3 (0.0, 0.5)* | −0.005 (−0.011, 0.001) |
| 28–34 wk (n = 99) | 19.0 (−20.8, 58.9) | 0.7 (−1.5, 3.0) | −0.2 (−0.8, 0.3) | −0.5 (−1.9, 1.0) | 0.2 (−0.1, 0.5) | 0.2 (−0.1, 0.6) | −0.004 (−0.010, 0.002) |
Models 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, attained 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), 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). AC, abdominal circumference; BPD, biparietal diameter; EFW, estimated fetal weight; FL, femur length; HC, head circumference; HL, humerus length.
Sample size decreases due to early deliveries. Sample size is consistent across fetal growth outcomes.
EFW outcome estimated at 15 wk, not 14 wk; EFW is not calculated before 15 wk.