Table 2. The results of stepwise regression analysis for weight and height/length.

	weight										height/length
	gestational age		parity		sex		birth order		zygosity		gestational age		parity		sex		birth order		zygosity
	R2 (%)	p	R2 (%)	p	R2 (%)	p	R2 (%)	p	R2 (%)	p	R2 (%)	p	R2 (%)	p	R2 (%)	p	R2 (%)	p	R2 (%)	p
birth	39.78	**	1.91	**	0.88	**	0.76	**	0.08	*	36.56	**	1.09	**	1.33	**	0.25	**	0.11	*
3 months	12.28	**	-	n.s.	7.34	**	0.47	**	-	n.s.	18.03	**	0.18	*	6.91	**	0.16	*	-	n.s.
6 months	3.44	**	0.63	**	8.21	**	0.53	**	-	n.s.	6.24	**	0.44	*	10.46	**	-	n.s.	-	n.s.
9 months	4.36	**	0.32	*	8.18	**	0.43	*	-	n.s.	6.30	**	-	n.s.	8.03	**	-	n.s.	-	n.s.
1 year	3.98	**	-	n.s.	8.66	**	-	n.s.	-	n.s.	6.22	**	-	n.s.	6.07	**	-	n.s.	-	n.s.
2 years	1.17	**	-	n.s.	8.32	**	-	n.s.	-	n.s.	1.61	**	-	n.s.	5.99	**	-	n.s.	-	n.s.
3 years	0.69	**	-	n.s.	4.16	**	-	n.s.	-	n.s.	0.84	**	-	n.s.	2.49	**	-	n.s.	-	n.s.

*: p<0.05, **: p<0.01.

None of the other variables (maternal and paternal age upon the birth of the twins, presentation, the birth year of the twins, or subject group) met the 0.05 significance level for entry into the model.

R²: coefficient of determination