Table 2.

Description of study samples ($n=722$ and 445), Puberty Cohort, Denmark, 2017.

Covariates	Sample 1 ($n=722$)	Missing (%)	Sample 2 ($n=445$)	Missing (%)
Sex, n (%)	—	0 (0)	—	0 (0)
Male	356 (49.3)	—	235 (52.8%)	—
Female	366 (50.7)	—	210 (47.2%)	—
Parity, n (%)	—	0 (0)	—	0 (0)
First child	342 (47.4)	—	215 (48.3)	—
Second or more child	380 (52.6)	—	230 (51.7)	—
Maternal age at delivery in years, $\text{mean}\pm \text{SD}$	$30.8\pm 4.3$	0 (0)	$31.1\pm 4.5$	0 (0)
Maternal age at menarche, n (%)a	—	7 (1.0)	—	3 (0.7)
Earlier than peers	175 (24.5)	—	123 (27.8)	—
Same time as peers	410 (57.3)	—	242 (54.8)	—
Later than peers	130 (18.2)	—	77 (17.4)	—
Highest social class of parents, n (%)b	—	2 (0.3)	—	1 (0.2)
High-grade professional	171 (23.8)	—	113 (25.5)	—
Low-grade professional	254 (35.3)	—	154 (34.7)	—
Skilled worker	203 (28.2)	—	119 (26.8)	—
Unskilled worker	92 (12.8)	—	58 (13.1)	—
Daily number of cigarettes in first trimester, n (%)	—	5 (0.7)	—	2 (0.5)
Nonsmoker	564 (78.7)	—	288 (65.0)	—
0–0 cigarettes/d	128 (17.9)	—	117 (26.4)	—
$>10$ cigarettes/day	25 (3.5)	—	38 (8.6)	—
Alcohol units/wk in first trimester, n (%)	—	0 (0)	—	0 (0)
0 units	385 (53.3)	—	168 (37.8)	—
$>0–1\text{unit}$	241 (33.4)	—	108 (24.3)	—
$>1–3\text{units}$	77 (10.7)	—	48 (10.8)	—
$>3\text{units}$	19 (2.6)	—	121 (27.2)	—
Prepregnancy BMI (${\mathrm{kg}/\mathrm{m}}^2$), n (%)	—	21 (2.9)	—	5 (1.1)
$<18.5$	26 (3.7)	—	26 (5.9)	—
18.5 to $<25$	479 (68.3)	—	286 (65.0)	—
25 to $<30$	155 (22.1)	—	88 (20.0)	—
$30+$	41 (5.8)	—	40 (9.1)	—
7-y BMI (${\mathrm{kg}/\mathrm{m}}^2$), $\text{mean}\pm \text{SD}$	15.6 (1.7)	191 (26.5)	15.5 (1.8)	99 (22.2)

Note: —, data not available; BMI, body mass index; SD, standard deviation.

^aMaternal age at menarche (AAM) reported in years. If unable to specify in years, then asked to report at which grade or, lastly, whether AAM was experienced earlier, same time, or later than peers. Observations with information in years or grade recategorized as earlier, same time, or later than peers according to national values from the Danish Ministry of Education.

^bBased on the International Standard Class of Occupation and Education classification system (ISCO-88 and ISCED codes) from Statistics Denmark.