Exposure of pregnant women to environmental tobacco smoke has been shown to be associated with low birth weight. Many studies have suggested that stress have a role in the etiology of preterm birth.

This study carried out from June 2008 to March 2009 to find the relation between environmental tobacco smoke, stress and miscarriage and preterm births.

A total of 33 subjects consisted of multiparous pregnant women that were in their early third trimester were chosen for this investigation. Subjects were divided into test group women with adverse pregnancy outcome, control group women with successful pregnancy. Four ml of unstimulated whole saliva were collected. The concentrations of cotinine and cortisol were evaluated using commercially available ELISA kit.

Pregnancies in which the average standardized cortisol during history of previous miscarriage(s) which occurred within 6th–27th week or/and history of preterm labor which occurred within 28th–36th weeks of gestation, demonstrated higher cortisol level (1.0201 ± 0.1855 ng/ml) compared to control group 0.9757 ± 0.2860 ng/ml (P = 0.323); statistical analysis showed no significant differences. Women of control group were more likely to be environmental tobacco smoke exposed (1.2714 ± 1.7639 ng/ml) than women with miscarriage and preterm births (0.9889 ± 0.5498 ng/ml).

The results from this primarily study demonstrated no association between cotinine, cortisol, miscarriage and preterm births.