Table 2. Unadjusted and adjusted hazard ratios (HRs) with 95% confidence intervals (CI) of colorectal cancer in relation to birth weight and birth length in the cohort analyses of Swedish like-sexed twins born in 1926–1958.

	Study population	Colorectal cancer		HR (95% CI), adjusted for
Birth weight, g	N	n	%	Birth characteristicsa (n=22 240)	Birth and maternal characteristicsb (n=16 703)
<2500	8904	86	1.0	1.01 (0.72–1.40)	1.07 (0.69–1.64)
2500–2999	8444	86	1.0	1.00	1.00
⩾3000	5989	76	1.3	1.15 (0.82–1.61)	1.04 (0.66–1.64)

Birth length, cm				(n=22 097)	(n=16 649)
<47	7220	68	0.9	0.94 (0.65–1.34)	0.92 (0.58–1.47)
47–49	6761	79	1.0	1.00	1.00
⩾50	9183	101	1.1	0.88 (0.64–1.20)	0.72 (0.48–1.09)

All analyses are stratified by birth year and have accounted for the clustered data structure and between-cluster effect.

^aAdjusted for zygosity, sex and gestational age.

^bAdjusted for birth characteristics, mother's age, parity and socioeconomic status at birth.