Newborns' cord blood plasma cotinine concentrations are similar to that of their delivering smoking mothers.

Abstract

In utero exposure to constituents of tobacco smoke has perinatal and postnatal health consequences. Umbilical cord plasma cotinine levels have been shown to correlate with self-reported daily number of cigarettes at the end of pregnancy, but the exact relationship between maternal and newborn plasma cotinine (and nicotine) is unknown. Concentrations of cotinine, nicotine's main metabolite, were determined in venous blood of delivering mothers and in arterial umbilical cord blood of their newborns at birth. Data from eighteen mother-newborn dyads were analyzed. The mothers smoked 95.1 (SD=96, range 10-420) cigarettes the week preceding delivery. Their mean plasma cotinine concentration at delivery was 106 ng/mL (SD=53, range 17-245) and the newborns' mean umbilical cord plasma cotinine was 88.2 ng/mL (SD=53, range 10-198, p<0.001). The difference can be explained by the elimination time of around 6h which occurred between sampling in mothers and in umbilical cord blood. Arterial umbilical cord blood plasma cotinine was highly associated with that of the smoking mothers: y=0.79x+0.97, Rsq=0.95, p<0.001. Maternal and newborn plasma cotinine concentrations are strongly associated. There is probably no placental barrier for plasma cotinine between pregnant mothers and their newborns. Lack of a placental barrier for cotinine (and probably nicotine) can partially explain smoking related perinatal disorders.