Figure 2.

Adjusted predicted risks of four adverse perinatal outcomes by gestational weight gain z score among women with twin gestations who are underweight (n=1,858, A), normal weight (n=26,011, B), overweight (n=13,373, C), grade 1 obese (n=7,153, D), grade 2 obese (n=3,684, E), or grade 3 obese (n=2,757, F), Pennsylvania twin birth certificates, 2003–2013. The solid lines represent the point estimate and dashed lines represent its 95% confidence bands. Vertical dotted lines represent the current Institute of Medicine provisional gestational weight gain guidelines for twin pregnancies.^8,11 Gestational weight gain z scores have been converted to equivalent total weight gain at 37 weeks of gestation on the y-axis. Tick marks and values of total weight gain are given for z scores of −2, −1, 0, 1, and 2 standard deviations. Risks were set at the population average for maternal race or ethnicity, maternal education, maternal age, marital status, parity, insurance source, smoking during pregnancy, preexisting diabetes or hypertension, height, prepregnancy weight, infertility treatment, infant sex, neonatal care level of birth facility, year of birth, urban residence, and racial composition of neighborhood.