Table 1.

Characteristics of Nurses’ Health Study II participants by duration of oral contraceptive (OC) use in 1989 (n=110,929)^a

	Duration of oral contraceptive use
	Never (n=18,994)	≤6 months (n=9,770)	>6 months-1 year (n=9,065)	>1-<5 years (n=36,026)	5-<10 years (n=27,800)	10-<15 years (n=7,857)	≥15 years (n=1,417)
Mean (Standard deviation)
Age (years)b	34.4 (4.6)	35.3 (4.6)	35.1 (4.6)	34.7 (4.8)	34.4 (4.7)	35.2 (3.9)	37.3 (3.1)
Age at menarche (years)	12.4 (1.5)	12.5 (1.5)	12.4 (1.5)	12.4 (1.4)	12.4 (1.4)	12.4 (1.4)	12.2 (1.5)
Body mass index (kg/m2)	24.5 (5.6)	24.1 (5.1)	24.0 (5.0)	24.1 (5.0)	23.9 (4.7)	23.7 (4.6)	24.0 (4.7)
Number of pregnancies ≥6 monthsc	2.2 (1.0)	2.2 (1.0)	2.2 (0.9)	2.1 (0.9)	1.9 (0.8)	1.7 (0.7)	1.5 (0.6)
Breastfeeding (months)c, d	14.7 (13.9)	13.3 (12.6)	12.8 (12.2)	12.5 (12.1)	10.9 (10.6)	8.3 (8.2)	6.4 (5.5)
Percentage
Ever parous	61	75	75	77	73	58	34
Infertilitye,f	15	20	21	21	17	11	6
Other current contraceptive methodg
IUD/diaphragm	17	16	15	13	11	7	6
Male contraception	32	33	33	32	28	22	15
Other contraception	23	20	19	17	14	12	8
Ever tubal ligation	10	16	15	18	18	13	7
Endometriosish	3	4	5	4	4	4	6
Ever migraines	12	16	16	16	15	15	16
Simple hysterectomyi	2	3	3	3	3	2	1
Family history of breast and/or ovarian cancer	8	8	7	7	7	7	11
Smoking status
Never smoker	77	68	66	65	59	54	56
Current smoker	9	12	13	13	16	20	22
Past smoker	14	20	21	22	25	26	22
Race
White	89	90	92	94	94	92	91
Asian	5	3	2	1	1	1	0
Other	6	7	6	5	5	7	9
Marital statusj
Married	68	78	79	82	80	72	56
Divorced/widowed	5	8	9	9	11	14	21
Never married	27	14	12	9	9	14	23

^aalues are standardized to the age distribution of the study population.

^bValue is not age adjusted

^cAmong parous women

^dMissing breastfeeding duration among parous women (n=13,845)

^eInfertility defined as trying to get pregnant for more than 1 year

^fMissing infertility (n=142)

^gIUD=Intrauterine device, male contraception includes vasectomy and male condoms, other contraception includes sponge, foam, rhythm method, and other contraception

^hLaparoscopically-confirmed endometriosis

ⁱMissing simple hysterectomy status (n=918)

^jMissing marital status (n=257)