URV researchers show for the first time that passive smoking affects the cognitive development of children in the same way as active smoking

The harmful effects that smoking during pregnancy has on child development are well known. Even so, of all the drugs, tobacco is the one that is most widely consumed in this period. A group of researchers belonging to the group NUTRISAM-Nutrition and Mental Health, from the URV departments of Psychology and Basic Medical Sciences, have shown that these effects are also produced when women are passively exposed to tobacco smoke in their environment.

The study included 158 mothers and their children. During pregnancy, both active and passive smoking, and the consumption of other drugs were recorded by means of termly questionnaires. Once the children had been born, their behaviour was evaluated after 48 hours and their cognitive development was monitored at 6, 12 and 30 months.

Forty-eight hours after birth, the children of mothers who smoked or were passive smokers presented greater muscle tension, excitability and irritability than the children of mothers who did not smoke or who had given up smoking at the beginning of their pregnancy. According to the researchers, these signs can be regarded as a symptom of the immaturity of the central nervous system. At 6, 12 and 30 months differences were also detected in cognitive development since the children of smokers and passive smokers had worse scores on the development of language. At 6 and 12 months they had greater difficulty in babbling, repetition and sound discrimination, prelinguistic vocalizations, first words, etc. And at 30 months (2 and a half years) they showed more difficulties in expressive and receptive language.

The researchers explain that, regardless of whether smoking is active or passive, nicotine passes into the mother’s bloodstream, goes through the placenta and directly affects the fetus’s central nervous system, which develops during gestation. In parallel, smoking causes arterial hypertension in the mother, which hinders the blood flow between the mother and the fetus. This leads to less oxygen and less nourishment, which often means that children are born underweight.

The importance of this research lies in the fact that many variables were taken into account that may also be related to the effects of active and passive smoking during pregnancy on cognitive development (for example, the anxiety of the mother during pregnancy, the type of birth, birth weight , gestational age, the psychopathology of the parents, passive exposure of the child to smoke and the socioeconomic level. The results of the study also showed that the children of mothers who give up smoking in the first term of pregnancy have the same psychosocial, demographic and cognitive characteristics as the children of mothers who had never smoked or who had given up before the pregnancy. This reinforces the importance of giving up smoking as soon as the mother knows she is pregnant.

Bibliographic reference: Carmen Hernández-Martínez, Núria Voltas, Blanca Ribot, Victoria Arija, Joaquín Escribano, Josefa Canals. “Effects of Prenatal Nicotine Exposure on Infant Language Development: A Cohort Follow Up Study”. Maternal and child health journal. July 2016. DOI: 10.1007/s10995-016-2158-y