. Author manuscript; available in PMC: 2014 Nov 1.

Published in final edited form as: Am J Prev Med. 2013 Nov;45(5):10.1016/j.amepre.2013.06.018. doi: 10.1016/j.amepre.2013.06.018

Table 3.

Associations between vehicle safety features and pregnancy outcomes among pregnant drivers in crashes, North Carolina, 2001–2008

	Preterm birth					Stillbirth

	Preterm births	Pregnancy days	Rate^a	aRR	95% CI	Still births	Pregnancy days	Rate^a	aRR	95% CI

Belt use^b
Belted	2661	2,181,498	122.0	1.00	Reference	133	2,557,126	5.2	1.00	Reference
Unbelted	50	35,685	140.1	1.13	0.86, 1.51	6	41,930	14.3	2.77	1.22, 6.28
Missing	67	51,004				3	59,591
Airbag availability^c
Equipped	2207	1,839,611	120.0	1.00	Reference	110	2,158,029	5.1	1.00	Reference
Not equipped	531	405,906	130.8	1.03	0.92, 1.14	30	474,509	6.3	0.91	0.58, 1.44
Missing	40	22,670				2	26,109

	Placental abruption					Premature rupture of the membranes

	Placental abruptions	Pregnancy days	Rate^a	aRR	95% CI	PROMs	Pregnancy days	Rate^a	aRR	95% CI

Belt use^b
Belted	178	2,557,126	7.0	1.00	Reference	569	2,557,126	22.3	1.00	Reference
Unbelted	3	41,930	7.2	1.06	0.34, 3.31	11	41,930	26.2	1.18	0.65, 2.15
Missing	5	59,591				15	59,591
Airbag availability^c
Equipped	137	2,158,029	6.3	1.00	Reference	483	2,158,029	22.4	1.00	Reference
Not equipped	45	474,509	9.5	1.58	1.08, 2.30	108	474,509	22.8	0.95	0.75, 1.20
Missing	4	26,109				4	26,109

Unadjusted rates per 100,000 pregnancy days

Rate ratios adjusted for maternal age, prenatal care initiation

Rate ratios adjusted for maternal age, seat belt use, vehicle model year

aRR, adjusted rate ratio; PROM, premature rupture of the membranes