Expired air carbon monoxide concentration in mothers and their spouses above 5 ppm is associated with decreased fetal growth.

Background: Smoking during pregnancy is associated with reduced birthweight; this relation can be reversed by smoking cessation. Some but not all previous studies have shown that smoking reduction (measured as cigarettes/day or urinary cotinine) may also improve birthweight. The relationship between maternal and spouses' expired air carbon monoxide (CO) concentrations (EACO) on fetal growth has not yet been evaluated.