A low second-to-fourth digit ratio (2D:4D) is a purported biomarker of increased intrauterine androgenic exposure, presumably linked to postnatal behavior. We aimed to examine the associations between 2D:4D and adolescence behavior problems expected from high (externalizing and attention problems) or low (internalizing problems) prenatal androgen exposure. We conducted a cross-sectional study of 1042 Colombian schoolchildren aged 11–18 y. We examined whether caliper-assessed 2D:4D was associated with behavior problems per the Youth Self-Report questionnaire. Mean problem standardized score point differences were estimated between hand- and sex-specific quintiles of 2D:4D with use of multivariable linear regression. Lower right-hand 2D:4D was associated with decreased externalizing and internalizing behavior problem scores. Corresponding lowest-to-median quintile adjusted mean differences (95% CI) were −4.6 (−7.5, −1.7) and −3.5 (−6.4, −0.6) points in boys; and −3.4 (−5.9, −0.9) and −3.5 (−6.2, −0.8) points in girls. Lower right-hand 2D:4D was also related to less attention and thought problems in boys, and to less social problems among girls. Associations were nonlinear, apparent only below 2D:4D medians, and stronger with the right than the left hand. In conclusion, right-hand 2D:4D is related to behavior problems in adolescence in directions that are not fully consistent with an androgenic exposure origin.

The 2nd--4th finger ratio (2D:4D) has been proposed as a potential indicator of greater androgen exposure during fetal development. Maternal periconceptional smoking may alter the homeostasis of fetal androgens, which could in turn result in differential development of 2D:4Ds in utero. The aim of the present study was to assess the effect of maternal periconceptional smoking (i.e. 1 year before through the first trimester of pregnancy) on the 2D:4D of children within The Maternal-Infant Research on Environmental Chemicals (MIREC) study. Maternal smoking history was obtained through questionnaires during the first trimester of pregnancy in 2001 women from 10 cities across Canada. The periconceptional smoking prevalence was 12%. A follow-up study was conducted to measure growth and development up to 5 years of age in a subsample of some 800 MIREC children (MIREC-CD Plus), and digital pictures of the ventral surface of both hands were obtained in mothers and children (2–5 years). The 2D:4D was calculated as the ratio of the 2nd and 4th fingers of each hand. Boys had lower mean 2D:4Ds compared with girls in both hands. Age and maternal 2D:4D were strong determinants of the children’s 2D:4D, however, the mean 2D:4D did not differ among children whose mothers had smoked during the periconceptional period compared with those who had not, irrespective of sex. In conclusion, we did not find an association between maternal periconceptional smoking and children’s 2D:4D, although the smoking prevalence was low.