This is established by modulation of maternal immune system and although no clear mechanism has been reported implicating progesterone in this action,11it has been reported that decidualization of the endometrium depends on adequate progesterone level together with endometrial expression of PR to mediate its effect.23A decline in serum progesterone and estrogen has also been reported in women with early spontaneous miscarriage compared with women presenting for elective termination of pregnancy.24 Here, PGR is linked to spontaneous abortion.