An Investigation into the Relationship between Second and Fourth Digit (2D:4D) Ratio in Multiple Births Women - A Case Study of Igbo-Ora, Nigeria

Prenatal exposure to Testosterone and Oestrogen predicts human finger length and the ratio of 2D:4D reflects sexual differentiation at an early age. Women with high 2D:4D ratio were found to have high reproductive success and this prompted us to find out if any, the relationship between digit ratio (2D:4D) and multiple births. Two hundred and One hundred voluntary female subjects from Igbo-Ora and Ogbomosho respectively, aged 25-50years who had given up on childbearing were grouped into four: Group I: Mothers who had given birth to Twins in Igbo-Ora (Identical and Non-Identical Twins, n=105). Group II: Mothers who had never given birth to Twins / Single birth mothers in Igbo-Ora, n=95. Group III: Mothers who had given birth to Twins in Ogbomosho (Identical and Non-Identical, n=50). Group IV: Mothers who had never given birth to Twins / Single birth mothers in Ogbomosho, n=50.The relaxed adducted fingers were flexed at metacarpo-phalageal joint at an angle 900 and placed on the table edge, after which the length of the second (2nd) and fourth (4th) fingers were measured from the second (2nd) and fourth (4th) mid metarcarpo-phalangeal joints to the tips of the second (2nd) and fourth (4th) fingers respectively for both hands and their ratio gave the Anatomical 2D:4D ratio while for Conventional measurements, the relaxed adducted fingers were placed in supine position on the table and the length of the second (2nd) and fourth (4th ) fingers were measured from the middle of the ventral proximal phalangeal crease to the tip of the second (2nd) and fourth (4th) fingers respectively of each hands of all the subjects and the ratio gave the Conventional 2D:4D ratio. The 2D:4D ratio of 800 fingers (2 fingers from each hand of 200 subjects) of Igbo-Ora subjects were compared with the 2D:4D ratio of the 400 fingers (2 fingers from each hand of 100 subjects) of Ogbomosho subjects both anatomically and conventionally. Measurements were done by two research assistants with vernier caliper at different times and the mean values were recorded as the reading. The digit ratio (2D:4D) was greater in single births women than in multiple births women in both Igbo-Ora and Ogbomosho subjects. This study showed that women with low 2D:4D digit ratio had high reproductive success which was contrary to previous belief. It is recommended that the research be carried out in a larger population.

Key Words: Testosterone, Oestrogen, 2D:4D ratio, Igbo-Ora, Multiple births