Low vitamin D levels during pregnancy linked to childhood obesity in boys

In a recent study published in the journal Nutrients, researchers examine the associations between prenatal vitamin D levels and growth and adiposity late in childhood.

Study: Prenatal Vitamin D Levels Influence Growth and Body Composition Until 11 Years in Boys. Image Credit: Danijela Maksimovic / Shutterstock.com

Pregnancy and Vitamin D

Vitamin D deficiency in pregnancy has been recognized as a public health concern and is considered a modifiable early risk factor for several conditions, including obesity.

Previous studies have reported associations between prenatal vitamin D deficiency and poor fetal outcomes. Although cross-sectional studies have linked deficient vitamin D levels to the risk of being overweight/obese in adolescents and children, evidence for the causal role of prenatal levels of vitamin D in the childhood development of obesity is insufficient.

About the study

The present study examined associations between maternal vitamin D levels in early-mid pregnancy and growth and body composition in children aged 11 or younger. The researchers included data from four regions, including Valencia, Gipuzkoa, Sabadell, and Menorca of the Spanish population-based birth cohort.

Individuals aged 16 or older with singleton pregnancy and intentions for delivery in the reference hospital were eligible for inclusion. Plasma levels of 25-hydroxyvitamin D₃ were quantified by high-performance liquid chromatography (HPLC). Weight and height were measured, whereas BMI and sex- and age-standardized z-scores were calculated.

Tetrapolar bioelectrical impedance analyses were performed. Fat-free mass was determined, with body fat values derived from the total weight.

Five BMI z-score trajectories were estimated using the latent class growth analysis. BMI polygenic risk scores (PRSs) were calculated for offspring of European ancestry using a reference genome-wide association study (GWAS) of BMI from the United Kingdom Biobank.

Linear regression was performed between BMI z-scores at seven years and individual PRSs, adjusting for the first 10 principal components. The PRS with the best fit was used for further analyses. Maternal and offspring characteristics were obtained using questionnaires administered during pregnancy or when the child was one year old.  

General additive models were used to evaluate the association between vitamin D₃ levels in pregnancy and various outcomes. Multivariable linear regression was performed to compute β-coefficients and 95% confidence intervals for the associations between prenatal vitamin D₃ levels and offspring outcomes. Multivariate logistic regression estimated the association between binary outcomes.

Study findings

Overall, 2,027 females had vitamin D measurements in pregnancy, with data on at least one growth or body composition outcome at seven or 11 years. Mothers were predominantly Spanish and about 30 years old at delivery.

Nearly 25% of mothers were obese or overweight before pregnancy. Mothers with deficient levels in pregnancy were younger, less educated, and smoked more during pregnancy.

Boys were more likely to be overweight at seven and 11 years than girls. Conversely, the mean fat mass was higher in girls at 11 years than in boys.

About 32% of children were average size at birth, with slower gain in BMI. Increased genetic predisposition to a high BMI was associated with a high BMI, fat mass percentage, and the prevalence of being overweight.

Deficient prenatal vitamin D₃ levels were associated with higher BMI z-scores at seven and 11 years. Children born to mothers with vitamin D deficiency in pregnancy had higher odds of being overweight; however, this effect was not statistically significant.

Associations of prenatal vitamin D₃ levels with child body composition outcomes were stronger in boys than in girls. Continuous vitamin D₃ levels in pregnancy were not associated with BMI z-score trajectories.

Deficient prenatal vitamin D levels were associated with a higher and lower risk of having a lower birth size and faster BMI gain in boys and girls, respectively. Furthermore, prenatal vitamin D deficiency in only normal-weight mothers was associated with increased body fat percentage in their offspring at 11 years.

The associations between vitamin D deficiency, fat mass percentage, and being overweight at 11 years were more robust in boys with an increased genetic predisposition to a high BMI.

Conclusions

Prenatal vitamin D levels were associated with body composition outcomes in boys. More specifically, vitamin D₃ deficiency was associated with increased BMI z-score, fat mass percentage, and the likelihood of being overweight, whereas these associations were inconsistent in girls.

The researchers also provided evidence that the genetic predisposition to a high BMI in boys might influence the observed associations. Therefore, prenatal vitamin D levels might be an early-modifiable risk factor for preventing childhood overweight.