Table II.

Characteristics of Women Participating in the British National Child Development Study, 1958-2001.

		All women included in analysis (n=6477)		Women with at least one pregnancy (n=5198)		Women with TTP data (n=4677)
		N*	%	N	%	N	%
Cohort member's mother's age at cohort member's birth
	0-<20	342	5.6	277	5.6	244	5.5
	20-<28	2998	48.9	2472	50.2	2246	50.7
	28-<35	2011	32.8	1568	31.9	1407	31.7
	>=35	785	12.8	605	12.3	536	12.1
Cohort member's mother's education
left school at minimum age		4562	74.5	3683	75.0	3316	74.9
schooling beyond minimum age		1560	25.5	1229	25.0	1109	25.1
Marital status at age 33
	married	4062	70.7	3794	76.2	3507	77.3**
	living with partner	659	11.5	536	10.8	483	10.7
single, divorced, widowed		1027	17.9	651	13.1	547	12.1
BMI at age 33
	<20	585	10.5	491	10.1	434	9.8
	20<25	3020	54.0	2610	53.9	2389	54.1
	25-<30	1325	23.7	1178	24.3	1085	24.6
	>=30	660	11.8	563	11.6	506	11.5
Smoking at age 33
	never	2861	49.5	2399	48.0	2199	48.4**
	former	1017	17.6	913	18.3	850	18.7
	current	1898	32.9	1683	33.7	1497	32.9
Education at age 33
	primary or less	855	14.3	678	14.2	574	13.3**
	secondary school	1272	21.3	1037	21.7	929	21.6
	O-levels or equivalent	1888	31.7	1554	32.5	1419	33.0
	A-levels or equivalent	780	13.1	614	12.9	571	13.3
	university or higher	1166	19.6	894	18.7	812	18.9
Childhood adversity and fertility
Social class (occupational) at age 33
I (managerial/professional)		201	3.7	154	3.3	142	3.3
	II	1547	28.2	1242	26.2	1148	26.5
III (manual/non-manual)		2371	43.2	2068	43.7	1887	43.6
	IV	1115	20.3	1030	21.8	934	21.6
	V	250	4.6	241	5.1	219	5.1
Age at 1 st pregnancy
	<20			827	16.1	717	15.3**
	20-<25			1769	34.3	1637	35.0
	25-<30			1500	29.1	1404	30.0
	30-<35			749	14.5	688	14.7
	>=35			307	6.0	231	4.9

TTP, time-to-pregnancy

^*May not sum to total due to missing data

^**Statistical difference (p<0.05) between those with TTP and without