Roe are a monoestrous species of deer.In season only once in a year.This is usually July/August.
The doe goes off patch finds a buck, lures him back to her area and then runs him ragged before mating.She normally goes around in a circle for a prolonged period before being mated. ( Evidenced by so called roe rings on the ground ) On a successful mating the blastocyst develops to the +/- 30 cell stage and then stops merely lying free in the uterus ( womb ).As a result of ovulating a corpus luteum ( yellow body ) is formed in the ovary. Note this is not a sign on pregnancy only that she has ovulated. During the last 6 weeks of the diapause, December/ January, the blastocyst elongates to the 100 cell stage. The conceptus ( Embryo plus associated membranes ) undergoes a period of rapid growth lasting 10-25 days. During this time a pregnancy associated glycoprotein ( PAG, a sugar attached to protein ) is produced by the conceptus. PAG production is inherent in the blastocyst without any triggering factor from the dam. However this PAG sets off a cascade leading to a dramatic increase in oestrodiol levels in the dam which is followed by implantation in the uterus and a successful pregnancy to birth April/May/June. Although sporadic reports of earlier births Pregnancy period 10 months.This enables the doe and young to have maximum nutrition available.
No cases of freemartinism has been reported in Roe in multiple births.
Orignal work by Lambert et al . Presented at various scientific congresses