Smoking During Pregnancy Linked to Obesity in Offspring  

C. Vidyashankar, MD

DELHI (Reuters Health) Aug 22 - Children whose mother's smoke during pregnancy are predisposed to obesity, researchers from Germany report.

Dr. Andre Michael Toschke and colleagues from the Ludwig-Maximilians-University in Munich evaluated 8765 school children between 5 and 7 years of age from the Bavarian region. Height, weight and body mass index was measured in the children, and the mothers completed a questionnaire on details of smoking before, during and after pregnancy.

A body mass index percentile greater than 90 was used to define overweight and a body mass index of greater that 97 was considered obese. The findings are reported in the August issue of the European Journal of Pediatrics.

A positive history of smoking during pregnancy was found in 660 mothers, and smoking before but not during pregnancy was found in 1542 mothers. Two hundred forty-four mothers started smoking after pregnancy, while 1139 of the 1542 mothers who had smoked before pregnancy resumed smoking after pregnancy, the researchers report.

The prevalence of obesity among children of mothers who smoked throughout pregnancy was 6.2%. For mothers who smoked before pregnancy or before and after pregnancy, the prevalence of obesity in their offspring was 4.5%. For women who smoked only after pregnancy, obesity in their offspring was 1.6%. Obesity in children of nonsmokers was 2.8%.

Compared with children of nonsmokers, the adjusted odds ratio for obesity was 1.92 among children of mothers who smoked throughout pregnancy, and 1.74 among those whose mothers smoked before and after but not during pregnancy, the researchers note.

Compared with non-smoking mothers, low birth weight deliveries were twice as common and breast-feeding rates less than half among mothers who smoked throughout pregnancy, the researchers note.

Exposure to nicotine during pregnancy may affect the dopamine and serotonin neurotransmitter systems in the growing fetus and lead to changes in the feeding and satiety reflexes, Dr Toschke and colleagues postulate. This can result in a suppression of satiety leading to overeating and obesity, they add.

While low birth weights are a likely consequence of smoking-related placental vasoconstriction in the last trimester, "metabolic imprinting" in the fetus due to maternal smoking early in pregnancy could be responsible for obesity in childhood, Dr. Toschke told Reuters Health.

"Since smoking after pregnancy was not associated with childhood obesity, intrauterine exposure rather than family lifestyle factors associated with smoking appears to be instrumental," the researchers conclude.