It has been hypothesized that increased incidence of reproductive abnormalities in human males is related to increasing exposures in-utero to endocrine disrupters especially estrogens and androgen receptor blockers.The male to female (M/F) ratio at births has been decreasing in the last few decades in several industrialized countries including Japan.On the other hands, the male to female fetal death ratio in Japan from the mid 1970s to 2005s has consistently increased while total fetal deaths have declined.This trend has not been explained.To investigate the causes for this trend, we paid attention to the point that the Wolffian duct, which development is androgen dependent, plays an important role for the male genesis as well as kidney genesis.Therefore, we investigated the trend of the congenital anomalies of the kidney and urinary tract (CAKUT) and other trend of infant and fetal deaths.For this purpose, public health records and other evidence were reviewed to assess the recent trends in infant renal failure, 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.The contaminated Japanese fetal environment,full of endocrine disruptive chemicals, might have affected to increase male fetal deaths.