. 2012 Apr 3;27(6):1649–1656. doi: 10.1093/humrep/des109

Table II.

Association between parental infertility and HB, USA, 2000–2008.

	All birthweights combined						Birthweight ≥2500
	Controls n (%)	Cases n (%)	OR^a	95% CI	OR^b	95% CI	Controls n (%)	Cases n (%)	OR^a	95% CI	OR^b	95% CI
History of infertility^c
Yes	109 (28.4)	82 (21.4)	0.74	0.52, 1.06	0.73	0.51, 1.07	56 (23.1)	52 (17.2)	0.70	0.45, 1.10	0.69	0.43, 1.10
No	275 (71.6)	301 (78.6)	Ref .		Ref .		186 (76.9)	251 (82.8)	Ref .		Ref .
Time to index pregnancy
Not trying	133 (34.6)	155 (40.5)	Ref .		Ref .		88 (36.4)	124 (40.9)	Ref .		Ref .
<12 months	192 (50.0)	177 (46.2)	0.84	0.60, 1.18	0.89	0.62, 1.29	129 (53.3)	150 (49.5)	0.89	0.61, 1.30	0.98	0.65, 1.49
12+ months	59 (15.4)	51 (13.3)	1.01	0.63, 1.64	1.05	0.61, 1.81	25 (10.3)	29 (9.6)	0.98	0.52, 1.84	0.97	0.49, 1.94
Doctor visit for infertility
Yes	62 (16.1)	48 (12.5)	0.94	0.60, 1.48	1.07	0.64, 1.78	23 (9.5)	27 (8.9)	1.08	0.58, 2.00	1.06	0.54, 2.08
No	322 (83.9)	335 (87.5)	Ref		Ref		219 (90.5)	276 (91.1)	Ref		Ref
Use of infertility drugs
Yes	45 (11.7)	34 (8.9)	0.92	0.55, 1.54	1.12	0.61, 2.04	12 (5.0)	20 (6.6)	1.57	0.73, 3.38	1.70	0.71, 4.06
No	339 (88.3)	349 (91.1)	Ref		Ref		230 (95.0)	283 (93.4)	Ref		Ref
Use of ART
Yes	20 (5.2)	16 (4.2)	0.94	0.44, 1.98	1.44	0.59, 3.54	3 (1.2)	7 (2.3)	2.07	0.50, 8.50	2.21	0.46, 10.70
No	367 (94.8)	367 (95.8)	Ref		Ref		240 (98.8)	296 (97.7)	Ref		Ref

^aAdjusted for matching factors only (birthweight, year of birth (quartiles), gender).

^bAdjusted for birthweight, year of birth (quartiles), gender, maternal age, maternal education, maternal race, plurality and gestational age.

^cEver try for one year or more.