Association of Prenatal Sex Steroid Exposure Estimated by the Digit Ratio (2D:4D) with Birth Weight, BMI and Muscle Strength in 6- to 13-year-old Polish Children

Objectives: The aim of this paper was to provide evidence for the impact of prenatal sex steroid exposure on prenatal and postnatal body size parameters, and muscle strength in children.

Methods: The following anthropometric data were studied in a group of 1148 children (536 boys and 612 girls) aged 6-13 years: the 2D:4D digit ratio, birth weight and length, and birth head and chest circumference. Postnatal parameters (6-13 years) included body weight and height, BMI, waist and hip circumference, WHR, as well as grip strength in both hands. All parameters that required it were adjusted for sex and gestational or chronological age. A general linear model, Pearson's correlation, t-statistics and Cohen's Δ were used in statistical analysis.

Results: Among birth size parameters, only birth weight was significantly negatively correlated with the 2D:4D digit ratio in children. Higher (feminized) digit ratios were significantly correlated with postnatal parameters such as body weight, BMI, and waist and hip circumference (positively), as well as hand grip strength-a proxy for muscular strength (negatively).

Conclusion: Problems with maintaining adequate body size parameters and muscle strength may be programmed in fetal life and predicted on the basis of the 2D:4D digit ratio. Body weight at birth and in early ontogenesis are additive correlates of the 2D:4D ratio. The present findings suggest that the 2D:4D digit ratio is related to postnatal phenotypes such as birth weight, overweight, and obesity as well as muscle strength in 6-13-year-old children of both sexes.