Table 3. Odds ratios (OR) and 95% confidence intervals (CI) for odds of obesity in first-born children by family size.

	Copenhagen School Health Records Register (Obese: ≥95th percentile)						Draft Board (Obese: BMI ≥31.00 kg/m2)
	Crude			Adjusted1,2			Crude			Adjusted1,3
First-born children* vs.	OR	95% CI	p-value	OR	95% CI	p-value	OR	95% CI	p-value	OR	95% CI	p-value
Any later born children (n1 = 12 035+12 469, n2 = 194+570)	0.73	[0.65–0.82]	0.006	0.89	[0.78–1.03]	0.121	0.73	[0.53–1.01]	0.057	0.81	[1.18–2.61]	0.209
Later born children in families with 2 children (n1 = 8 014+6128, n2 = 194+198)	0.67	[0.58–0.78]	<0.001	0.81	[0.68–0.96]	0.017	0.73	[0.48–1.11]	0.144	0.7	[1.10–2.54]	0.257
Later born children in families with 3 children (n1 = 3 044+4 334, n2 = 61+159)	0.85	[0.67–1.07]	0.169	1.05	[0.79–1.40]	0.724	0.84	[0.44–1.62]	0.606	0.85	[1.37–3.66]	0.658
Later born children in families with 4 children (n1 = 744+1 464, n2 = 9+72)	0.50	[0.32–0.79]	0.003	0.76	[0.44–1.33]	0.338	1.48	[0.37–5.96]	0.583	1.33	[0.61–1.99]	0.696

^*Excluding only children.

¹Adjusted for birth weight, birth year,

²Adjusted for maternal age when giving birth, sex, maternal BMI (age 13 years),

³Adjusted for father’s social class. n₁ = number in the CSHRR, n₂ = number in the DB.