. Author manuscript; available in PMC: 2011 Jul 1.

Published in final edited form as: Arthritis Rheum. 2010 Jul;62(7):1842–1848. doi: 10.1002/art.27459

Table 3.

Adjusted relative risks of RA by gravidity and parity, and by parity within age subgroups

Age (years)	Parity	Controls (N = 1418) N (%)	Cases (N = 310) N (%)	RR^* (95% CI)
All	Nulligravid	228 (16)	68 (22)	1.0
	Gravid, nulliparous	81 (6)	29 (9)	1.20 (0.72 – 2.00)
	Parous	1109 (78)	213 (69)	0.61 (0.43 – 0.86)
< 35	Nulliparous	151 (53)	58 (67)	1.0
< 35	Parous	136 (47)	29 (33)	0.54 (0.33 – 0.90)
35 – 44	Nulliparous	98 (20)	24 (30)	1.0
35 – 44	Parous	383 (80)	56 (70)	0.52 (0.30 – 0.90)
45 – 54	Nulliparous	36 (12)	8 (12)	1.0
45 – 54	Parous	262 (88)	59 (88)	1.00 (0.44 – 2.29)
55 – 64	Nulliparous	24 (7)	7 (9)	1.0
55 – 64	Parous	328 (93)	69 (91)	0.79 (0.32 – 1.96)

for all ages, adjusted for age, race (white vs. non-white) and oral contraceptive use (ever vs. never); within age subgroups, adjusted for race and education level (college or more vs. less than college).