Increase in male fetal deaths in Japan and congenital anomalies of the kidney and urinary tract

The male to female (M/F) fetal death ratio in Japan from the mid 1970s to 2005s has consistently increased while total fetal deaths have declined. Public health records and other evidence were reviewed to assess the recent trends in infant renal failure, the congenital anomalies of the kidney and urinary tract (CAKUT), and the sex ratio of these disorders. The M/F infant death ratio caused by renal failure has increased from 0.75 to 3.0 over the past 3 decades. There has been an increase in CAKUT as a cause for fetal and infant deaths, and renal hypoplasia and dysplasia were male predominant. The increase in the M/F deaths ratio caused by infant renal failure, as well as increased male predominant CAKUT suggests that the Wolffian duct regression might have affected the initial development of the kidney and male genital tract thus contributing to male fetal deaths.