The male/female ratio of fetal deaths and births in Japan.

The decline in the male/female ratio of births has not yet been explained. In Japan, the male/female ratio of fetal deaths has been increasing since the 1970s, reaching over 2.0 in 1996. The increased male/female ratio of births could explain the decrease In the male/female ratio of births during the past two decades. This trend could suggest the increasing prenatal vulnerability of the male fetus especially at earlier stages of gestation.