ABSTRACT
Removal of the corpus luteum before the end of the seventh week of amenorrhea leads to miscarriage. Rescue can be achieved with progesterone therapy but not with estrogen. Corpus luteum deficiency has been cited as the underlying pathology in 35%–40% of unexplained recurrent pregnancy losses, manifesting in low serum progesterone levels and out-of-phase endometrial biopsies. Progesterone may modulate the immune response required to achieve a successful pregnancy outcome. In human pregnancy, serum samples from patients with infertility and paid volunteers were evaluated for both progesterone-induced blocking factor and progesterone at various times of the cycle, whether natural or involving embryo transfer after endogenous and exogenous progesterone exposure and after various synthetic progestins. Treatment was commenced in the PROMISE trial as soon as pregnancy was diagnosed. The role of the PROMISE study was to assess progesterone, and not other progestogens. Other progestogens should be assessed, as progestogens do not have a class action, and each has different pharmacological actions.
