Is There Any Possible Relationship Between Antenatal Hydronephrosis and Prenatal Androgen Exposure? An Analysis Using the 2D:4D Digit Ratio

Abstract

Objectives The ratio of the index finger to the ring finger length (2D:4D) differs between sexes; it is typically higher in females than in males. This difference is thought to be related to intrauterine androgen exposure. Antenatal hydronephrosis is the most frequently detected anomaly during prenatal ultrasonographic evaluation of fetal development. This study aims to investigate the relationship between the 2D:4D ratio in newborns and the presence of congenital hydronephrosis. Methods Between July 2023 and April 2024, the lengths of the second and fourth digits and medical birth records of newborns were documented. Infants who were followed antenatally for hydronephrosis and exhibited persistent findings on postnatal renal ultrasonography were included in the study group. The control group consisted of newborns without any antenatal or postnatal renal abnormalities. Results A total of 82 newborns were included in the analysis. Among them, 50 had no antenatal or postnatal renal anomalies and comprised the control group. In 32 newborns, both antenatal and postnatal hydronephrosis were diagnosed. The 2D:4D was significantly higher in the hydronephrosis group compared to the control group (p < 0.001). No significant differences were found between right and left hand 2D:4D measurements within either group (p > 0.05). Conclusion The observation of significantly higher 2D:4D ratios in newborns with antenatal hydronephrosis may suggest a possible association with decreased prenatal androgen exposure. While the 2D:4D ratio is generally expected to be higher in females and lower in males, the finding of higher ratios in newborns with hydronephrosis may indicate a reduced androgen effect during fetal development in these cases. Although this finding is consistent with the fact that hydronephrosis is more frequently observed in male fetuses, it should be interpreted with caution and supported by further studies.