Table 1

Breakdown of participation showing the number of complete twin pairs for whom all the red cell indices and genotype information (in the case of dizygotic pairs) were available

12 years	14 years	16 years	MZF	MZM	DZF	DZM	DZOS	Total
DZF, dizygotic females; DZM, dizygotic males; DZOS, dizygotic twin pairs of opposite sex; MZF, monozygotic females; MZM, monozygotic males.
√			19	28	9	11	18	85
	√		8	5	2	4	7	26
		√	46	54	14	11	40	165
√	√		28	26	26	37	60	177
√		√	4	3	4	1	7	43
	√	√	8	10	5	7	13	19
√	√	√	41	35	31	33	51	191
Total			154	161	91	104	196	706
Total at 12 years			92	69	71	82	136	450
Total at 14 years			85	76	64	81	131	437
Total at 16 years			99	102	54	52	111	418