Table 1.

Demographic Characteristics of Women in the Three Studies

	Study #1 1989 to 1991 (N = 7,178) N (%)	Study #2 1991 to 1992 (N = 2,230) N (%)	Study #3 2002 to 2004 (N = 3,118) N (%)
Age (yrs) (mean, sd)	(26.3, 5.8)	(26.2, 6.4)	(27.9, 6.2)
< 21	1317 (18)	512 (23)	446 (14)
21–25	1982 (28)	574 (26)	714 (23)
26–30	2170 (30)	513 (23)	821 (26)
31–35	1235 (17)	431 (19)	751 (24)
36 +	462 (6)	192 (9)	374 (12)
Missing	12 (0)	8 (0)	12 (0)
Race
Native Am	185 (3)	101 (5)	132 (4)
Asian	575 (8)	223 (10)	294 (9)
Black	891 (12)	409 (18)	358 (11)
Hispanic	241 (3)	112 (5)	171 (5)
White	5126 (71)	1306 (59)	1994 (64)
Other	154 (2)	71 (3)	59 (2)
Missing	6 (0)	8 (0)	110 (4)
Education (yrs) (mean, sd)	(12.7, 2.3)	(12.8, 2.5)	(13.8, 2.7)
< 12	1595 (22)	510 (23)	428 (14)
12–15	4384 (62)	1301 (59)	1719 (56)
16 +	1145 (16)	394 (18)	935 (30)
Missing	54 (1)	25 (1)	36 (1)
Marital
Unmarried	2868 (40)	1125 (50)	1152 (37)
Married	4293 (60)	1097 (49)	1948 (62)
Missing	17 (0)	8 (0)	18 (1)
Parity (mean, sd)	(1.9, 1.2)	(1.9, 1.2)	(2.0, 1.2)
1	3244 (46)	1042 (47)	1357 (44)
2	2122 (30)	641 (29)	973 (32)
3	1081 (15)	305 (14)	436 (14)
4 +	634 (9)	223 (10)	298 (10)
Missing	97 (1)	19 (1)	54(2)
Smoking
Nonsmoker	4435 (62)	1392 (62)	2258 (72)
Smoker	2564 (36)	767 (34)	777 (25)
Missing	179 (2)	71 (3)	83 (3)