The second-to-fourth digit (2D:4D) ratio is a sexually dimorphic trait, with men having lower ratios than women, indicating relatively higher prenatal testosterone exposure compared to oestrogen. The 2D:4D ratio is fixed in intrauterine conditions that are affected by foetal sex steroids (testosterone and oestrogen) and an indirect method to determine intrauterine sex hormone levels that significantly correlate with somatic features, behavioural traits, fertility measures, reproductive characteristics, and predisposition to certain chronic diseases. Researchers discovered that a more masculine (low 2D<4D) digit ratio and a more feminine (high; 2D>4D) digit ratio are manifestations of increased prenatal testosterone and oestrogen exposure, respectively. Furthermore, digit ratio (2D:4D) values are widely used to predict reproductive capacity and success, fertility measures, natural menopause, and age at menarche, which varies between populations. The current review paper attempted to discuss sexual dimorphism in 2D:4D ratios, as well as its potential association and utility in evaluating certain reproductive characteristics and behavioural traits in populations. Methodological comparisons, benefits and drawbacks of determining the 2D:4D for studying the effect of prenatal sex steroids are also highlighted.