Table 1.

Mean value ± s.d. (sample size) for each outcome variable for females having different configurations of younger and elder siblings. The significance (p-value) refers to comparisons with the reference category (none) in each independent variable (younger and elder siblings) for each reproductive factor. Where p-values are greater than or equal to 0.1, they are not provided in this table.

	sex configuration of siblings	age at menarche	age at first sexual intercourse	age at first pregnancy	number of pregnancies	age at first birth	number of children
younger siblings	none	13.2 ± 1.41 (63)	18.1 ± 2.15 (63)	26.5 ± 6.43 (62)	1.4 ± 1.66 (62)	28.4 ± 7.56 (62)	0.9 ± 1.23 (63)
	exclusively sisters	13.2 ± 1.21 (38)	18.3 ± 2.42 (38)	24.8 ± 5.60 (38)	1.1 ± 1.64 (38)	26.0 ± 5.59 (37)	0.8 ± 1.73 (38)
	exclusively brothers	12.8 ± 1.48 (45)	19.3 ± 2.94 (41) p = 0.012	25.4 ± 6.66 (42)	1.6 ± 1.99 (42)	27.1 ± 7.86 (45)	1.0 ± 1.43 (45)
	both brothers and sisters	12.9 ± 1.56 (39)	20.0 ± 6.51 (38) p = 0.016	24.7 ± 7.03 (38)	1.6 ± 1.99 (39)	26.4 ± 7.67 (38)	1.3 ± 1.70 (38)
elder siblings	none	12.7 ± 1.38 (71)	19.6 ± 5.41 (70)	25.2 ± 6.88 (68)	1.2 ± 1.75 (69)	26.7 ± 7.75 (70)	0.8 ± 1.27 (71)
	exclusively sisters	12.7 ± 1.42 (34)	17.9 ± 2.50 (33)	26.3 ± 5.94 (33)	1.4 ± 1.87 (33)	27.3 ± 5.71 (33)	0.9 ± 1.37 (33)
	exclusively brothers	13.6 ± 1.35 (42) p = 0.006	18.9 ± 2.51 (39)	23.7 ± 4.41 (40)	1.4 ± 1.69 (40)	25.4 ± 7.21 (41)	1.1 ± 1.39 (42)
	both brothers and sisters	13.3 ± 1.39 (35)	18.8 ± 2.29 (35)	27.7 ± 7.50 (36)	1.9 ± 1.97 (36)	30.2 ± 7.43 (36)	1.4 ± 1.66 (36)