TABLE 2

Age at Achievement of Gross Motor Milestones in Infancy and Total Developmental Scale Score at Age 4 Years: Upstate KIDS Study

MilestoneModel 1Model 2Model 3
B (95% CI), PB (95% CI), PB (95% CI), P
Singletons (n = 314)
 Sitting without support−34.0 (–57.9 to –10.1), .01−36.0 (–62.3 to –9.6), .01−17.6 (–40.7 to 5.4), .14
 Hands-and-knees crawling−29.6 (–52.6 to –6.6), .01−29.2 (–54.0 to –4.5), .02−12.5 (–34.9 to 9.9), .28
 Standing with assistance−42.1 (–63.2 to –21.0), <.001−42.6 (–64.5 to –20.7), <.001−21.9 (–41.5 to –2.2), .03
 Standing alone−23.2 (–52.0 to 5.7), .12−28.5 (–59.7 to 2.7), .08−6.2 (–35.2 to 22.9), .68
 Walking with assistance−35.5 (–58.7 to –12.4), .003−42.7 (–67.6 to –17.8), <.001−19.6 (–42.7 to 3.5), .10
 Walking alone−25.9 (–52.8 to 0.9), .06−28.4 (–31.5 to –0.1), .05−5.4 (–31.5 to 20.7), .69
Twins (n = 259)
 Sitting without support−2.6 (–28.3 to 23.1), .848.4 (–18.7 to 35.4), .557.8 (–19.0 to 34.6), .57
 Hands-and-knees crawling2.5 (–18.5 to 23.4), .829.9 (–13.8 to 33.6), .4111.7 (–10.6 to 34.0), .30
 Standing with assistance−3.9 (–29.5 to 21.6), .765.0 (–23.4 to 33.4), .736.1 (–20.0 to 32.1), .65
 Standing alone−29.2 (–54.0 to –4.4), .02−23.6 (–53.2 to 5.9), .12−21.4 (–47.1 to 4.3), .10
 Walking with assistance−27.7 (–47.7 to–7.8), .01−18.3 (–40.0 to 3.4), .10−10.9 (–34.7 to 13.0), .37
 Walking alone−15.5 (–40.5 to 9.6), .23−11.3 (–37.2 to 14.6), .39−8.1 (–28.9 to12.7), .44
  • Developmental skills were assessed by using the BDI-2. Model 1: adjusted for maternal age, education, race, prepregnancy BMI, smoking, drinking, being married, having private insurance, having older sibling for the child, and a child’s sex, age, and day care attendance before 12 months. Model 2: additionally adjusted for gestational age and birth weight. Model 3: additionally adjusted for developmental screening status and exposure to infertility treatment. Descriptions of each milestone are given in Supplemental Table 5.