Table 1.

Characteristics of the Avon Longitudinal Study of Parents and Children (ALSPAC) nested case-control study population (N = 367 mother-daughter dyads).

	Menarche < 11.5 years (N = 172)		Menarche ≥ 11.5 years (N = 195)		P-value for difference^a
Characteristic	N	%	N	%
Child race					0.61
White	159	95.8	182	96.8
Non-white	7	4.2	6	3.2
Maternal education^c					0.39
< O-level	36	21.7	32	16.8
O-level	56	33.7	62	32.5
> O-level	74	44.6	97	50.8
Maternal age at menarche, years					< 0.0001
8–11	50	33.3	23	13.9
≥12	100	66.7	142	86.1
Maternal pre-pregnancy BMI, kg/m²					0.0004
< 25 (under/normal weight)	113	72.4	159	87.8
≥25 (overweight/obese)	43	27.6	22	12.2
Prenatal vegetarian diet					0.92
Yes	10	6.1	11	5.9
No	154	93.9	177	94.1
Prenatal smoking					0.47
Any	29	17.3	27	14.4
None	139	82.7	160	85.6
Maternal age at delivery, years					0.63
< 25	32	18.7	35	17.9
25–29	71	41.5	73	37.4
≥30	68	39.8	87	44.6
Child birth order					0.03
First born	101	61.6	97	51.6
Second born	36	22.0	66	35.1
Third born or later	27	16.5	25	13.3
Child birth weight, g^d					1.00^b
< 2500	<5	–	<5	–
≥2500	166	–	188	–
Breastfeeding duration, months					0.04
Not breastfed	26	16.0	38	20.8
<3	53	32.5	35	19.1
3–5	26	16.0	34	18.6
≥6	58	35.6	76	41.5
Use of infant soy formula^d					0.43^b
Any	<5	–	<5	–
None	163	–	187	–
Vegetarian diet during childhood					0.65
Yes	8	4.8	7	3.8
No	158	95.2	176	96.2
Childhood BMI Z-score					< 0.0001
<0	32	20.9	60	34.5
0–1	50	32.7	77	44.3
≥1	71	46.4	37	21.3
Gestational age at sample, weeks	Median	IQR	Median	IQR	0.04^e
	12.0	7.5–17.0	13.0	9.0–18.0
Age at menarche, years
	11.0	10.7–11.3	12.8	12.3–13.4

Abbreviations: g, grams; kg/m², kilograms per meter-squared; IQR, interquartile range.

Compared using chi-square tests unless otherwise noted.

Compared using Fisher’s exact test.

< O-level = none, Certificate of Secondary Education, and vocational education, which are equivalent to no diploma or a GED in the United States. O-levels (ordinary levels) are required and completed at the age of 16. > O-level=A-levels (advanced levels) completed at 18, which are optional, but required to get into university; and a university degree.

Counts and percents suppressed due to small cell sizes.

p-value for difference between cases and controls using the Wilcoxon Rank Sum Test.