The ratio between the length of second and fourth digits (2D:4D) is a putative biomarker for prenatal testosterone and estrogen exposure. The aim of the study was to examine the association between 2D:4D and women's general and reproductive health. This analysis was conducted within a prospective pregnancy cohort study. The study population included 187 women. 2D:4D was measured directly in both hands using a digital caliper. Multivariable linear and logistic models were used to study the associations between digit ratio and the studied health characteristics. Mean age of the participants was 30.7 ± 4.9 years. The mean age at menarche was 12.9 ± 1.4 years. Right hand 2D:4D mean ± SD was 0.965 ± 0.03. Left hand 2D:4D mean ± SD was 0.956 ± 0.03. An association was found between right 2D:4D and age at menarche, with older age in women with 2D:4D ≥ mean versus 2D:4D < mean (13.2 ± 1.5 and 12.8 ± 1.3 respectively, b = 0.48, 95%CI:0.06-0.91) while controlling for ethnicity. Higher 2D:4D was also associated with heavier menses bleeding and dysmenorrhea. There is an association between 2D:4D and sub optimal reproductive characteristics, including later age at menarche, heavier menses bleeding and dysmenorrhea. These findings support the association between the intrauterine period and reproductive characteristics. further studies are required to support our findings. The ratio between lengths of the second and the fourth digits (index and ring fingers) (2D:4D) is a putative biomarker of prenatal testosterone and estrogen exposure 1. 2D:4D is sexually dimorphic, and males' 2D:4D is relatively shorter than females' 2,3. 2D:4D is observed at as early as the end of the first trimester 4,5. Relative digit length is considered steady at ages 2 to 25 6 , although other studies suggest that 2D:4D does mildly increase during childhood but remains steady during puberty 7,8. 2D:4D was suggested to be associated with Hox gene family 2,3. Homeobox genes Hox a and Hox d may indirectly influence the prenatal production of androgen by controlling the differentiation of the urogenital system as well as digit development. Considering this, it was suggested that there may be an association between prenatal hormonal function and digit formation, and 2D:4D was proposed as an indicator of first trimester testosterone and estrogen levels, reflecting the Hox genes' action on differentiation 9,10. Environmental exposure to toxicants is critical during early development stages, such as the perinatal period, in which there is a heightened vulnerability to exposures due to potential permanent effect on health and development 11. Previous research showed association between prenatal hormonal environment and exposure to endocrine disrupting chemicals and 2D:4D in animals 12,13 and humans 2,10,14-16. Conversely, some studies found no support for such association 17-19. Assessing the prenatal hormonal environment directly from the fetus in utero is challenging because of the risk for the fetus. Therefor other methods have been used to evaluate prenatal ...