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. 2022 Aug 9;12(1):13586.
doi: 10.1038/s41598-022-17247-3.

Digit ratio (2D:4D) and maternal testosterone-to-estradiol ratio measured in early pregnancy

Gareth Richards #  1 , Ezra Aydin #  2   3 , Alex Tsompanidis  4 , Eglė Padaigaitė  5 , Topun Austin  6   7 , Carrie Allison  4 , Rosemary Holt  4 , Simon Baron-Cohen  4
Affiliations

Digit ratio (2D:4D) and maternal testosterone-to-estradiol ratio measured in early pregnancy

Gareth Richards et al. Sci Rep. .

Abstract

The ratio of index to ring finger (2D:4D) has been hypothesised to indicate prenatal androgen exposure, yet evidence for its validity is lacking. We report the first pre-registered study to investigate mothers' early pregnancy sex hormone concentrations in relation to their children's digit ratios measured at 18-22-month follow-up. Although the testosterone (T) to estradiol (E) ratio correlated negatively with right hand digit ratio (R2D:4D) and directional asymmetry (right-minus-left) in digit ratio (D[R-L]), neither effect remained statistically significant once demographic and obstetric covariates were controlled for. Nevertheless, the multivariate level of analysis did reveal that T correlated positively with left hand digit ratio (L2D:4D) and negatively with D[R-L]. However, the first of these effects is in the opposite direction to that predicted by theory. Taken together, the results of our study suggest research with larger samples is required to determine whether digit ratios are valid proxies for maternal sex hormone exposure.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Scatterplots showing the associations between maternal T:E ratio and children’s (a) R2D:4D, (b) L2D:4D, and (c) D[R−L]. Raw data (not controlled for covariates) are shown; T:E ratio is multiplied by 1000.
See this image and copyright information in PMC

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