Noninvasive validation of tobacco smoke exposure in late pregnancy using end-tidal carbon monoxide measurements

To determine whether exposure to tobacco smoke in late pregnancy can be reliably estimated by measuring carbon monoxide (CO) in the mother and newborn breath.

Sixty-eight mothers and their healthy term singleton newborns, delivered at a university-affiliated community hospital in Jerusalem, were enrolled. End-tidal CO (corrected for inhaled air [ETCOc] was measured with a portable automated bedside CO analyzer. ETCOc, cotinine, and carboxyhemoglobin (COHb) levels were compared in 17 smoking, 31 passively exposed, and 20 nonsmoking mothers and their offspring.

The mean +/- SD ETCOc was significantly higher in women who smoked than in passively exposed and nonsmoking mothers (8.42 +/- 5.65 vs 1.95 +/- 0.98 vs 1.33 +/- 0.84 ppm. p < 0.0001, respectively). Newborns whose mothers smoked had higher ETCOc levels than those of infants of passively exposed and nonsmoking mothers (10.0 +/- 7.7 vs 2.51 +/- 1.4 vs 1.74 +/- 0.98 ppm, p < 0.0001, respectively). The number of cigarettes smoked by the mother was significantly correlated with maternal ETCOc (r = 0.755, p < 0.00001), and neonatal ETCOc (r = 0.805, p < 0.00001). Maternal ETCOc was highly correlated with neonatal ETCOc (r = 0.857, p < 0.00001), cotinine (r = 0.645, p < 0.00001), and COHb (r = 0.9, p < 0.00001) levels. Birth weight was significantly associated with neonatal ETCOc (p < 0.006) and maternal ETCOc (p < 0.007).

ETCOc levels in the newborn are well correlated with maternal smoking. Measurements of newborn ETCOc may be used as a noninvasive means to estimate exposure to maternal tobacco smoke immediately before delivery. These measurements will be useful for patient education and research.