End-tidal carbon monoxide measurements in women with pregnancy-induced hypertension and preeclampsia

OBJECTIVE: We sought to compare the end-tidal carbon monoxide breath levels in pregnant women with and without pregnancy-induced hypertension and pree clampsia. STUDY DESIGN: We prospectively performed end-tidal carbon monoxide measurem ents corrected for ambient carbon monoxide in nonsmoking women during late gestation (>31 weeks). The study group included 22 women with pregnancy-ind uced hypertension or symptoms of preeclampsia and a control group of 20 nor motensive pregnant women. RESULTS: The carbon monoxide measurements corrected for ambient carbon mono xide (mean +/- SD) were significantly lower(P < .01) in the hypertensive gr oup than in the control group (1.17 <plus/minus> 0.35 vs 1.70 +/- 0.54 ppm) . The study group had a significantly higher number of low (<1.2 ppm) end-t idal carbon monoxide measurements corrected for ambient carbon monoxide (13 [59.1%] vs 1 [5.0%]; P < .001). The end-tidal carbon monoxide measurements corrected for ambient carbon monoxide remained significantly lower in comp arison with those found in the control group when the study group was divid ed into women with pregnancy-induced hypertension only (n = 11) and those w ith preeclampsia (n = 11) (1.19 +/- 0.37 ppm; P < .01;and 1.15 <plus/minus> 0.41 ppm; P < .01; respectively). CONCLUSIONS: Our findings suggest that carbon monoxide formation may be sig nificantly lower in women with pregnancy-induced hypertension and preeclamp sia. These data suggest that carbon monoxide could have a contributory role in the apparent paradox of the seemingly protective effect of smoking to d ecrease the risk of preeclampsia.