A new study shows that newborns that have been exposed to cigarette smoke from both active and passive smoking mothers show poor physiological, sensory, motor and attention responses.

Smoking during pregnancy has been linked to many different problems in infants like learning difficulties, attention deficit disorder with hyperactivity and even obesity. However, although the pediatric and obstetric disorders linked to tobacco during this stage are well defined, the effects on neonatal behaviour have not yet been studied in depth.

A new study headed by experts at the Behaviour Evaluation and Measurement Research Centre (CRAMC) of the Rovira i Virgili University and published in the journal Early Human Development goes further and analyses the effects of passive smoking during pregnancy on the newborn.

The scientists evaluated the behaviour of 282 healthy newborns using the Neonatal Behavioural Evaluation Scale. This allows for interaction with the newborn in order to evaluate its behaviour and responses between 48 and 72 hours after birth.

From those mothers studied, 22% smoked during pregnancy and about 6% were exposed only to second-hand smoke. Out of the smoking mothers, 12.4% had between 1 and 5 cigarettes a day; 6.7% had between 6 and 10 a day; and 2.8% had between 10 and 15 a day. None of them smoked more than 15 cigarettes a day.

"Newborns who have had intrauterine exposure to cigarette smoke, whether in an active or passive way, show signs of being more affected in terms of their neurobehavioural development. This could be an indicator of pathologies, independently of sociodemographic, obstetric and pediatric factors," as explained by Josefa Canals and Carmen Hernández, the lead authors of the study.

The results reveal that those born to smoking and passive smoking mothers score low in their ability to inhibit stimuli that could alter the central nervous system. Furthermore, children of passive smoking mothers have poor motor development and those of smoking mothers have less ability to regulate behaviour and response in physiological, sensor, motor and attention terms.

"Health professionals should encourage future mothers and their families to eliminate or reduce tobacco consumption," states Canals, who outlines the importance of informing mothers on the effects of involuntary exposure to cigarette smoke in order to prevent direct damage to the fetus and infant development.

Smoking during pregnancy

Smoking during pregnancy is one of the biggest yet changeable causes of illness and death for both mother and infant. Nonetheless, epidemiological studies show that between 11% and 30% of pregnant women smoke or are passively exposed to tobacco smoke.

When a pregnant woman smokes, nicotine concentrations in the fetus reach more than 15% of that of the mother. In Spain, 43.5% of women between 25 and 44 years of age smoke but this percentage during pregnancy falls to approximately 26.6%.

"However, although women tend to reduce their normal tobacco consumption when falling pregnant, the key is to study the effects of exposure to small amounts of smoke on fetal development," conclude Canals and Hernández.