ESPE Yearbook of Paediatric Endocrinology

Scientific Reports (2022)12:3135 doi: 10.1038/s41598-022-07122-6

Brief Summary: This case cohort study, based on the Danish National Birth Cohort (DNBC) with ~100 000 women and their children, investigated whether maternal smoking in pregnancy is associated with child BMI and risk for child overweight, independent of maternal pre-pregnancy BMI, genetic predisposition to adiposity and socio-economic factors. Furthermore, the authors assessed the interaction of maternal predisposition to adiposity on the association between maternal smoking on child BMI.

The study shows that any smoking during pregnancy is associated with higher child BMI at age 7 years. This association was weaker when adjusted for maternal BMI or maternal BMI GRS (genetic risk score) for BMI. Furthermore, smoking during pregnancy was associated with higher odds for childhood overweight in a dose-dependent manner: the odds ratio for ≧ 11 cigarettes/day in the third trimester was 2.42 (1.3–4.5; 95% confidence interval) compared to non-smoking, irrespective of maternal BMI or maternal GRS. In addition, there was no interaction between maternal GRS and smoking. The study is based on the very large Danish National Birth Cohort with more than 90 000 mother-child pairs allowing a unique study design with a follow-up time of 7 years. In addition, maternal genetic predisposition to adiposity was assessed as a GRS, and maternally-transmitted GRS could be analysed separately from non-transmitted (maternally-acting) GRS.

This study adds to previous evidence that the association between smoking during pregnancy and child overweight is not confounded by a genetic predisposition to adiposity of the mother. Furthermore, using a design with high statistical power, the study confirms that the effects of smoking during pregnancy on childhood adiposity are lasting at least up to 7 years. The mechanisms are unclear, possibly relating to in utero exposure on developing adipocytes or appetite-regulatory neurons, or consequent to the early rapid catch-up in growth and weight gain that is typically seen in these infants. However, they add support to public health efforts to eradicate smoking exposure during pregnancy.