Prenatal ultrasound study of gender difference in urinary tract morphology in normal fetuses

Objective: To compare gender difference on renal pelvic size and urinary bladder volume (BV) in normal male and female fetuses at 37 weeks of gestational age (GA) using ultrasound. Methods: 414 normal singleton pregnancies of 37 weeks GA were included. In each fetus, antero-posterior (AP) diameter of the renal pelvis and BV was measured. Results: Male fetuses were found to have greater AP diameter of renal pelvis than female (male: 2.69±0.93 mm and female: 2.46±0.87 mm) (p<0.05, independent sample t-test). Female fetuses were found to have a greater BV than male (male: 13.93±8.43 cm³ and female: 17.22±10.22 cm³) (p<0.05, independent sample T test). Conclusions: Gender difference in morphology indicates that the respective urinary tract development is different between male and female fetuses, which probably accounts for gender difference in the urinary tract anomalies detected during neonatal period.