Birth weight of Swedish boys stable despite obesity epidemic

Birth weight among Swedish boys has remained relatively stable during a 65-year period, despite the growing worldwide obesity epidemic, according to study findings presented at the European Obesity Summit in Gothenburg, Sweden.

The results contradict other studies showing an increasing birth weight in other countries, the researchers noted; however, those studies spanned a shorter period of time.

“Birth weight has been stable during the 65 years, with small, periodic fluctuations in mean birth weight and distribution,” Jimmy Celind, MD, of Sahlgrenska University Hospital in Gothenburg, and colleagues wrote. “The increases of mean birth weight reported by others between 1970 and 2000 is present in our data, but represents a periodic fluctuation in the long perspective of the present study.”

Jimmy Celind

Celind and colleagues analyzed child health care centers growth data, including birth weight, from centrally archived records for all boys born in 1945 or later in Gothenburg. The researchers established a population-based cohort, the BMI Epidemiology Study (BEST; n = 400,000). In this subanalysis of 14 birth cohorts, researchers analyzed birth weight of 400 consecutively first-born boys every fifth year from 1946 to 2011 (n = 5,600; mean birth weight, 3.5 kg).

Linear regression analysis between year of birth and birth weight was stable across the 65-year study period (P = .003). The 5th, 25th, 75th and 95th percentiles were all stable across the study period, and ORs for low, very low and high birth weight per birth year increment were 1.04, 1 and 0.99, respectively.

Adjustments for country of birth for the children’s parents did not alter results, according to researchers.

Celind said the findings show that the obesity epidemic has not resulted in an increase in birth weight, noting that the OR for high birth weight, although statistically significant, is clinically insignificant. “This study is important in the way that it changes the perception of increasing birth weights on a population basis,” Celind told Endocrine Today. “Hopefully, it will encourage further research in the area of fetal growth and lead to better understanding of human development. It will not change risks or guidelines regarding overweight/obesity entering or during pregnancy. If further research show that, for example, ambitious maternal health care programs can undo the impact of overweight and obesity on birth weight, it will probably lead to political interest and encourage further investments in this area.”

Celind said birth weight trends should be evaluated in longer perspectives internationally, either to verify his colleagues’ results or to show that the secular change in birth weight differs in other countries.

“The factors that reduce or eliminate the overweight/obesity effect on birth weights in the population need to be explored,” Celind said. – by Regina Schaffer

Reference:

Celind J, et al. Poster PP4.06. Presented at: European Obesity Summit; June 1-4, 2016; Gothenburg, Sweden.

Disclosure: Celind reports no relevant financial disclosures.