Table 2.

Associations between birth order and sibship composition with odds of overweight or obesity (BMI ≥85th percentile) including only biological siblings

	Unadjusted odds ratios (95% CI) (n = 273)	Odds ratios (95% CI) (n = 273) Adjusted for confounders only†	Odds ratios (95% CI) (n = 273) Adjusted for confounders and intermediate variables‡
Birth order category
Only child	3.22 (1.42, 7.30)**	3.68 (1.55, 8.68)**	4.18 (1.67, 10.46)**
Youngest sibling	2.00 (1.04, 3.79)*	2.71 (1.27, 5.77)**	3.21 (1.41, 7.33)**
Middle sibling	1.39 (0.67, 2.79)	1.68 (0.79, 3.61)	1.71 (0.76, 3.86)
Oldest sibling (reference)	1	1	1
Index child has ≥1 younger sibling
Yes	0.51 (0.31, 0.83)**	0.44 (0.26, 0.77)**	0.38 (0.21, 0.69)**
No (reference)	1	1	1
Index child has ≥1 older sibling
Yes	1.09 (0.67, 1.79)	1.24 (0.72, 2.16)	1.28 (0.71, 2.31)
No (reference)	1	1	1
Index child has ≥1 brother
Yes	0.50 (0.30, 0.81)**	0.49 (0.30, 0.81)**	0.47 (0.28, 0.81)**
No (reference)	1	1	1
Index child has ≥1 sister
Yes	1.11 (0.68, 1.79)	1.16 (0.71, 1.91)	1.10 (0.64, 1.89)
No (reference)	1	1	1

^*P-value < 0.05.

^**P-value < 0.01.

^†Models adjusted for potential confounders only: child sex, child age, child race/ethnicity, maternal age and maternal education.

^‡Models adjusted for potential confounders: child sex, child age child race/ethnicity, maternal age and maternal education and potential intermediate variables: maternal relationship status, household food insecurity, maternal depression symptoms, maternal BMI and birth weight z-score. BMI, body mass index; CI, confidence interval.