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

OBJECTIVE

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.

STUDY

DESIGN

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.

RESULTS

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).

CONCLUSION

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.