Effects of carbon monoxide air pollution in pregnancy on neonatal nucleated red blood cells

In an analytical cross-sectional study, the effects of carbon monoxide air pollution on carboxyhaemoglobin (COHb) and absolute nucleated red blood cells (nRBC) of the cord venous blood, were evaluated in 41 newborns delivered by caesarean section at term to mothers who had lived in an air-polluted area in the centre of Tehran during their pregnancies (study group). The parameters used were compared with 32 cord venous bloods of term caesarean-delivered newborns of mothers living in a healthy air area outside the city during their pregnancies. A significant difference was observed between the two groups in the cord COHb levels (mean +/- SD 10.51 +/- 4.79 vs. 1.58 +/- 0.96, P < 0.001), cord nRBC (723.87 +/- 275.23 x 10(6)/L vs. 248.44 +/- 160.79 x 10(6)/L, P < 0.001). A significant correlation was found between ambient carbon monoxide and cord COHb in the study and control groups, respectively (r = 0.863, P = 0.0001; r = 0.691, P = 0.0001), and also cord COHb and cord nRBC in the study group (r = 0.360, P = 0.01). Neonates born to mothers exposed to carbon monoxide air pollution had increased circulating absolute nRBC counts compared with those of the control group. We speculate that air pollution exposure in pregnancy should be avoided, because it may have negative effects on fetal oxygenation.