Daughters of Smoking Mothers Have More Gestational Diabetes

May 20, 2013

Women who were exposed to tobacco smoking in utero were more likely to develop gestational diabetes when they became pregnant, new research shows. They were also more likely to be obese than the offspring of women who didn't smoke during pregnancy, Kristina Mattsson, MD, from Lund University, Sweden, and colleagues say in their report, published online May 20 in Diabetologia.

Only 1 previous study has investigated this, say Dr. Mattsson and colleagues. The current work confirms the findings "in a large independent, population-based cohort…[with] a more accurate exposure assessment, as women were asked about their current tobacco use, thus avoiding…recall of distant events," they observe.

The results "support a strengthening of the recommendation of trying to get to those women who smoke during pregnancy and encourage, and help, them to quit," Dr. Mattsson told Medscape Medical News. "This is another adverse consequence that smoking could have, [and] the effects may persist longer than we thought earlier."

The results are doubly important because they come against a backdrop of numbers that "point to an increase in smoking among young women in some countries after years of decline," she added. "So [in our] quest to try to minimize pregnancy smoking, we have not yet reached our goal."

Fetal Tobacco Exposure Risks Extend Into Adulthood

Dr. Mattsson and colleagues used figures from the medical birth registers of Sweden for women born in 1982 (when smoking data were first registered) or later and who had given birth to at least 1 child themselves; 80,189 pregnancies were included.

The association between in utero smoking exposure was divided into 3 categories: never exposed, moderately exposed (1 to 9 cigarettes per day) and heavily exposed (more than 9 cigarettes per day).

Among the daughters studied, 7300 subsequently became obese and 291 developed gestational diabetes when they themselves became pregnant.

The adjusted odds ratio of gestational diabetes was increased among women who were moderately exposed (odds ratio [OR], 1.62) and heavily exposed (OR, 1.52) to tobacco in utero.

The OR for obesity was also similarly increased, at 1.36 and 1.58, for those exposed as a fetus to moderate and heavy amounts of tobacco, respectively.

A relation between pregnancy smoking and obesity in the offspring has been reported consistently, Dr. Mattsson and colleagues note. But regarding the continuance of this association into adulthood, the results "are conflicting," they observe.

The authors suggest possible mechanisms behind the link could be alterations in the regulation of appetite and satiety, which has been found in animal studies.

Other reported effects of prenatal nicotine exposure include a higher rate of death of the insulin-producing beta cells in the pancreas and increased gene expression of transcription factors, triggering formation of adipocytes, which could be involved in the development of diabetes and obesity, respectively.

In addition, they add that recent data show epigenetic changes in the offspring of smoking mothers, such that tobacco exposure could actually cause changes in the gene expression in the unborn child that could predispose them to later obesity or diabetes.

They caution, however, that although adjustments were made in the second-generation women for age, parity, mode of delivery, gestational age, birth weight, their own smoking during early pregnancy, and body mass index (adjusted for diabetes risk but not for obesity risk), they were unable to take into account other possible confounding factors.

These included educational level, income, and other socioeconomic determinants of health, something they point out is "perhaps the main weakness of this study."

In conclusion, "these data show that women exposed to smoking during fetal life are at higher risk of developing gestational diabetes and obesity in adulthood," they reiterate.

"Although short-term detrimental effects of smoking on the individual and her offspring are well-known, such associations might extend into adulthood, making the incentive stronger for undertaking [preventive] measures, particularly as numbers in some countries point to an increase in daily smoking among young women."

The authors have reported no relevant financial relationships.

Diabetologia. Published online May 20, 2013. Article

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