Smoking during pregnancy: changes and associated risk factors in Spain, 1980-2016

Trends for maternal smoking rates have varied substantially across industrialized countries. The objective was to describe how the prevalence of maternal smoking evolved in Spain during 1980-2016.

Data came from the Spanish Collaborative Study of Congenital Malformations. Our sample consisted of 40 934 mothers of newborns with no congenital defects from hospitals all across Spain. We estimated change points in trend and the mean annual change in smoking prevalence using 'joinpoint' regression. Relevant potential factors (age, country of birth, education, parity, planned pregnancy and alcohol consumption) were examined using multivariate logistic regression.

Maternal smoking prevalence in 1980 and 2016 were 14.3% (95% confidence interval [CI]: 11.9-17.0) and 20.4% (95% CI: 15.9-25.8). We identified four periods with distinct trends: a sharp increase during the 80s, a plateau during the 90s, a decrease starting in 2000 and a slowdown of such decrease from 2009 on. Smoking was significantly higher among young women, Spain-born, with low education, unplanned pregnancy, and alcohol consumption.

Currently in Spain maternal smoking remains very high. Tobacco consumption trend showed an increase during the 80s, a plateau during the 90s, and a reduction in the 2000s. Several sociodemographic and behavioural factors were associated to greater likelihood of smoking.