Biomarkers of fetal conditions: Finger ridge‐counts, facial fluctuating asymmetry, and digit ratio (2D:4D)—are they correlated in women?

Abstract

Objectives: Fetal environmental conditions are crucial for lifelong health. Direct measurements of developmental conditions are limited in humans; thus, several biomarkers of those conditions have been proposed: that is, finger ridge-counts, level of facial fluctuating asymmetry (FA), and digit ratio (2D:4D). Since all of these biomarkers share a similar gestational time of formation, we hypothesize that their values are significantly correlated. Materials and methods: Data were collected at the Mogielica Human Ecology Study Site in southern Poland among 234 women. Finger ridge-counts, level of facial FA, and 2D:4D have been measured. The two-step analyses included Pearson's correlations of simple values of the biomarkers and correlations of composite variables calculated based on principal component analysis. Results: We did not find any statistically significant correlations between finger ridge-counts, FA, and 2D:4D in women. Similarly, we did not observe any correlations between three composites created from the biomarkers. Discussion: Our results indicate that there are no relationships between the biomarkers, suggested as proxies of the quality of prenatal conditions, in a single population. This is the first study analyzing three different markers simultaneously. The lack of correlations may indicate that the tested biomarkers reflect, in fact, different environmental conditions, occurring in separate "critical windows" of development, or that the biomarkers are not valid as proxies of developmental conditions.

Finger ridge‐counts correlate with the second to fourth digit ratio (2d:4d)

“…Most basic is that the relationship of finger ridge‐counts with 2d:4d is complex and unlikely to be detected with summary variables such as TRC or ARC. The present results did not demonstrate a relationship with ARC, in line with similar findings reported by Dressler and Voracek (2011) and Klimek et al (2021) That is because ridge‐counts have numerous underlying processes that contribute to the phenotype, most of which are not significantly influenced by fetal hormones. The association between ridge‐counts and 2d:4d was not found in those principal components reflecting the largest proportion of variation in the covariance matrix.…”

“…Manning (2002, p. 11) reported a significant relationship between the ridge‐count on right digit 4 and 2d:4d on the right hand in a sample of very low birth weight individuals. However, attempts to demonstrate correlation between 2d:4d and ridge‐counts using variables such as summations of ridges over digits have been unsuccessful (Dressler & Voracek, 2011; Klimek et al, 2021), leaving the relationship unresolved.…”