Table 2.

Summary of Maternal ETS Exposure and Preterm Birth Studies

First Author	Year	Cohort Size	Location of Study	Exposure Assessment Method	ETS Exposure Definition	Association?	Odds Ratio
Martin12	1986	3891	USA: MA	In-person interview	Exposed more Than 2 hours per week	No	NO OR given: ETS exposed preterm birth rate: 4.64%; ETS non-exposed preterm birth rate: 4.66%
Mathai28	1992	994	India	In-person questionnaire	1 Household member smokes	No	NO OR; ETS exposure: 5–8% preterm birth rate; non-ETS exposed 3–8% preterm birth rate
Fortier14	1994	4644	Canada	Phone interview-Post pregnancy (up to 6 weeks)	Exposed more Than 1 hour per week	No	ETS exposed at work: 0.92 [CI: 0.64–1.31]
						No	ETS exposed at home: 0.93 [CI: 0.58–1.51]
						No	ETS exposed at home and work: 0.98 [CI: 0.56–1.73]
Windham17	2000	4454	USA: CA	Phone interview-Early pregnancy	Exposed more Than 1/2 hour per day	Yes (not significant)	Low ETS (05–6.5hrs/day) & Very Preterm (<35wks): 1.5 [CI: 0.90–2.5];
						Yes (not significant)	Low ETS (05–6.5hrs/day) & Preterm (<37wks): 1.1 [CI: 0.79–1.6];
						Yes (not significant)	High ETS (>7hrs/day) & Very Preterm (<35wks): 2.4 [CI: 1.0–5.3];
						Yes (not significant)	High ETS (>7hrs/day) & Preterm (<35wks): 1.6 [CI: 0.87–2.9]
Jaakkola26	2001	389	Finland	Questionnaire at Clinic - Post pregnancy & Maternal Hair nicotine-post pregnancy	<0.75ug/g Hair Nicotine concentration	Yes (not significant)	Hair Nicotine: (0.75-<4.00 ug/g): 1.30 [CI: 0.30–5.58]
						Yes	Hair Nicotine: (>4.00 ug/g): 6.12 [CI: 1.31–28.7]
						No	ETS at home: 0.65 [CI: 0.06–6.81]
						Yes (not significant)	ETS at work: 2.35 [CI: 0.50–11.1]
						Yes	ETS exposure home/work: 8.89 [CI: 1.05–75.3]
Kharazzi27	2004	3669	USA:CA	Questionnaire at Clinic - Post pregnancy & Maternal serum cotinine (15–19 Weeks pregnant)	<0.026 ng/ml Serum Cotinine concentration	No	Serum Cotinine: (0.026–0.053 ng/ml): 0.90 [CI: 0.48–1.66];
						No	(0.054–0.0096 ng/ml): 0.76 [CI: 0.40–1.42]
						No	(0.097–0.235 ng/ml): 0.68[CI: 0.35–1.30]
						Yes	(>0.235 ng/ml): 1.78 [CI: 1.01–3.13]
Ashford29	2010	210	USA: KY	Questionnaire and Hair maternal cotinine	Answered Yes to any exposure question	Yes (not significant)	ETS exposure: 2.3 [CI: 0.96–5.96]
Crane13	2011	11,852	Canada	Questions asked by physician at first prenatal visit	Any exposure-Cutoff not defined	Very Preterm (<34 Wks): Yes (not significant) ; Preterm (<37 Wks): Not reported	Very Preterm (<34 Wks): 1.87[CI: 1.00–3.53]
Qiu16	2013	10,094	China	In-person interview-Post pregnancy (1–3 days post-delivery)	Exposed more Than 1/2 hours per month	Yes	ETS During Whole Pregnancy: Very Preterm (<32Wks): 1.98 [CI: 1.41–2.27];
						No	Moderate Preterm (32–36wks): 0.98 [CI: 0.81–1.19]
						Yes (not significant)	Preterm (32–36wks): 1.12 [CI: 0.95–1.32]
Miyake15	2013	1565	Japan	2 questionnaires (1 during pregnancy, 1 post pregnancy)	At least 1 person in home or at work smoked during 1 st questionnaire	No	ETS at home: 0.91 [CI: 0.48–1.65]
						No	ETS at work: 0.97 [CI: 0.36–2.23]