Maternal smoking during pregnancy and nicotine and cotinine concentrations in maternal and neonatal hair

Conflicting data have been reported in the association between maternal smoking and adverse effects during pregnancy and in neonates. Some studies, conducted on a limited number of patients have evaluated maternal consumption and fetal exposure by measuring nicotine and cotinine in the hair. Our aims were to evaluate the relationship among maternal cigarette consumption, fetal smoking exposure and outcome of pregnancy in a population of pregnant women who smoked.

Mothers smoking during pregnancy were included at their first prenatal visit and followed prospectively. Maternal data (demographic variables, obstetrical history and cigarette consumption), neonatal data and birth indicators (number of weeks of gestation, type of delivery, weight) were collected. Hair samples from the mothers and the babies were collected at birth.

The present study was conducted in the Department of Obstetrics of the University Hospital Robert Debré in Paris.

A total of 254 women smokers were included in the study and 182 mother/neonate pairs were analyzed after exclusion of 50 babies whose hair samples were inadequate and 22 for various other reasons.

Nicotine and cotinine concentrations in the maternal and neonatal hair were measured at birth by radio-immunoassay.

Cigarette consumption was based on self reporting and quantified each trimester. It was expressed more precisely during the third trimester by the mean number per cigarette per day. Nicotine and cotinine concentrations in the maternal and neonatal hair at birth were also analysed.

Nicotine and cotinine concentrations in maternal hair were associated with cigarette consumption during the third trimester of pregnancy (P < 0.003 and P < 0.01, respectively). In neonates, only cotinine concentrations were associated to maternal cigarette consumption (P < 0.0001). This association remained significant in a multivariate analysis, which included maternal cotinine hair concentrations and the ethnic group.

Our results have shown a strong relationship between maternal cigarette consumption and fetal exposure to smoking measured by cotinine concentrations in neonatal hair. Further studies are required to look for associations between fetal exposure and adverse pregnancy outcome.