Table 2.

Odds ratios for pairs discordant for birth weight and ASD (and ASD-like traits) on the A-TAC using McNemar’s test.

Pairs		ASD	Restricted/ Repetitive	Language	Social
Overall	No. discordant pairs*	34	151	120	37
	No. lighter child meeting cut-off	26	92	80	26
	OR (95% CI)	3.25‡ (1.47, 7.18)	1.56‡ (1.12, 2.16)	2.00‡ (1.37, 2.92)	2.36† (1.17, 4.78)
MZ	No. discordant pairs*	7	38	41	8
	No. lighter child meeting cut-off	5	23	30	6
	OR (95% CI)	2.50 (0.49, 12.89)	1.53 (0.80, 2.94)	2.72‡ (1.37, 5.44)	3.00 (0.61, 14.86)
DZ	No. discordant pairs*	19	88	62	22
	No. lighter child meeting cut-off	14	54	41	15
	OR (95% CI)	2.80† (1.01, 7.77)	1.59† (1.03, 2.44)	1.95† (1.15, 3.30)	2.14 (0.87, 5.26)
Males	No. discordant pairs*	25	98	81	24
	No. lighter child meeting cut-off	18	63	52	16
	OR (95% CI)	2.57† (1.07, 6.16)	1.80‡ (1.19, 2.72)	1.79† (1.14, 2.82)	2.00 (0.86, 4.67)
Females	No. discordant pairs*	9	63	39	13
	No. lighter child meeting cut-off	8	29	28	10
	OR (95% CI)	8.00† (1.00, 63.96)	1.21 (0.70, 2.08)	2.55‡ (1.27, 5.11)	3.33 (0.92, 12.11)

OR=Odds Ratio; CI=Confidence Interval;

^*Discordant for birth weight and ASD (or ASD-like traits) on the A-TAC. Birth weight discordance defined as ≥ 400 gram difference in birth weight between the twins in a pair, or one twin at least 15% lighter than the other in the pair;

^†p≤0.05;

^‡p≤ 0.01.