Table 3.

Relative risk of preterm birth among singleton live births in three states, Massachusetts, Michigan, and Florida, 2000–2010: includes non-ART referent and ART mothers without female infertility diagnosis stratified by semen source

ART/male infertility by semen source	N (% PTB)	Relative risk crude (CI)	Relative risk adjusted (CI)a
Non-ART	4,370,361 (8)	Reference	Reference
ART/partner	5857 (9)	1.2 (1.1, 1.3)	1.4 (1.3, 1.5)
ART/donor	217 (10)	1.3 (0.9, 1.9)	1.4 (1.0, 2.1)

^aAdjusted for parity, age, race/ethnicity, education level, state of residence and delivery year

ART assisted reproductive technology, PTB preterm birth, CI confidence interval, singletons of subfertile male with missing semen source data were excluded (n = 1013)