Maternal smoking and the bilirubin concentration in the first three days of life.

The effect of maternal smoking on the plasma bilirubin concentration in the first three postnatal days was investigated in 137 mature newborns. Forty-three percent of the mothers reported on smoking during pregnancy. The median increase in plasma bilirubin concentration during the first 24 h of postnatal life was significantly higher in the group of neonates born to smokers compared to the group of neonates born to non-smokers (P less than 0.02). By contrast, the median increase in plasma bilirubin concentration from the 1st to the 3rd postnatal day was significantly lower among the neonates born to smokers compared to the group with non-smoking mothers (P less than 0.04). The overall frequency of clinical jaundice and the frequency of neonates with plasma bilirubin concentration above 175 microM on the 3rd postnatal day was almost identical in the two groups. It is suggested that maternal smoking may affect the postnatal plasma bilirubin concentration in the offspring by various mechanisms.