Table 2 Effect on age at menarche from prenatal and childhood factors

		Effect on age at menarche in months (95% CI)
Risk factor	Unit	Univariate (max. N =81 438)	Multivariate ( N =48 079) ^a
Birthweight	Per 500 g increase	0.31 (0.19, 0.43)^***	1.24 (1.10, 1.37)^***
Twinning (Ref. Singleton)	Same-sex DZ twin	1.36 (−0.13, 2.86)
	Opposite-sex DZ twin	1.75 (0.33, 3.17)^*
	MZ twin	2.03 (0.44, 3.62)^*
Maternal age at birth	Per 5-year increase	−0.08 (−0.20, 0.03)	0.36 (0.19, 0.53)^***
Pre-eclampsia or eclampsia (Ref. Not exposed)^b	Exposed	−1.31 (−1.93, −0.69)^***
Maternal smoking (Ref. Not exposed)^b	Exposed	−1.83 (−3.23, −0.43)^*
Number of weeks breastfed	Per 4-week increase	0.08 (0.01, 0.15)^*
Ethnicity (Ref. White)	Mixed white/non-white	−1.70 (−3.59, 0.20)	−1.39 (−3.81, 1.02)
	Non-white	−3.49 (−4.84, −2.13)^***	−7.80 (−9.90, −5.70)^***
Weight at age 7 years	Per increase in category^c	−5.07 (−5.23, −4.90)^***	−4.54 (−4.75, −4.33)^***
Height at age 7 years	Per increase in category^c	−3.48 (−3.62, −3.34)^***	−2.98 (−3.16, −2.80)^***
Childhood exercise	Per 10 h increase each week	1.51 (1.18, 1.84)^***	1.18 (0.78, 1.59)^**
Number of siblings	Per sibling	0.96 (0.87, 1.05)^***	1.45 (1.28, 1.61)^***
Birth order	Per increase in birth order	0.27 (0.15, 0.40)^***	−1.26 (−1.48, −1.03)^***
Vegetarian before age 8 years (Ref. No)	Yes	−1.33 (−3.27, 0.62)

Abbreviations: CI=confidence interval; DZ=dizygotic; MZ=monozygotic; Ref.=reference group.
^*P<0.05, ^**P<0.01, ^***P<0.001.
Effects were estimated using ordinary least squares regression.
^a The multivariate model was chosen using backward selection. Maternal smoking and number of weeks breastfed were not eligible for this model due to the large amounts of missing data for these variables.
^bPrenatal exposure to these factors.
^cSee Table 1 for a list of the weight and height categories.

Quick links

Search