Table 1.

Characteristics of mothers in the subcohort and mothers who developed preeclampsia, Collaborative Perinatal Project (1959–65).

	Subcohort n=3068 %	Preeclampsia cases n=717 %
Maternal race
White	49	38
Black	44	53
Puerto Rican	7	9
Parity
0	33	52
1 or more	67	48
Maternal age, years
<20	23	37
20–29	61	43
≥30	16	20
Prepregnancy body mass index, kg/m2
<18.5	10	9
18.5–24.9	72	64
25–29.9	14	18
≥30	4	9
Marital status
Married	81	67
Unmarried	19	33
Maternal education, years
≤8	16	23
9–11	37	39
12	33	30
>12	14	8
Socioeconomic status score
0–20	7	11
20–39	27	34
40–59	33	33
60–79	20	15
80–100	13	7
Smoking during pregnancy
Yes	53	35
No	47	65
Entry to prenatal care
<13 weeks	28	20
13–26 weeks	72	80
Gestational age of blood sampling
<13 weeks	13	8
13–<20 weeks	33	28
20–26 weeks	54	64
Season of blood sampling
Winter	23	26
Spring	26	25
Summer	26	25
Fall	25	24
Latitude of study site
≥41°N	61	50
38–40°N	31	39
≤35°N	8	11