Perturbations in finger length and digit ratio (2D:4D) in ICSI children

Intracytoplasmic sperm injection (ICSI) is used to overcome severe male-factor infertility where males are azoospermic or have poor quality spermatozoa. Perturbations of finger length (short finger length adjusted for height and high second-to-fourth digit ratio, or 2D:4D) have been described in azoospermic men and men who are rated as having low sexual attractiveness. High 2D:4D has been described in women with high fecundity. Such perturbations may be related to endocrine regulation of some homeobox genes. This study compared finger length and 2D:4D in singleton children conceived with the help of ICSI with those in naturally conceived singleton controls. Participants were recruited from centres in Germany and the UK. There were 211 children conceived by ICSI and 195 controls. Finger length was measured from photocopies of the ventral surface of the hand. In comparison to controls, male and female ICSI children had shorter fingers after correction for height. There was also evidence that female ICSI children may have higher 2D:4D than female controls. Perturbations in finger length in ICSI children may be inherited from their fathers and, in the case of boys, could be associated with lower fertility and reduced sexual attractiveness. For ICSI females, increased 2D:4D may be associated with increased fertility.