LUTEAL-PHASE SUPPORT

The luteal phase of IVF cycles are different than the luteal phases of naturally occurring cycles. These differences may stem from the act of mechanical disruption of the ovarian follicle but can be overcome by the administration of exogenous luteal phase support (Table 2). Direct progesterone supplementation can measurably increase luteal phase serum levels, and it appears that the route of administration and formulation of the compound may influence luteal serum progesterone levels. Because progesterone production begins within the ovarian follicle prior to ovum capture, the timing of initiating therapy appears somewhat flexible. Another effective method of luteal support, which does not appear to be superior to progesterone, is the administration of exogenous hCG (Table 3). The major risk of this form of therapy is exacerbation of ovarian hyperstimulation leading to severe OHSS. The duration of luteal support strives to cover the transition between corpus luteum function and complete placental hormone production. This transition may occur as late as the 12th gestational week, although placental function begins nearly 2 months earlier. The future of luteal phase support will center on the more elusive goal of improving pregnancy rates than on normalizing hormone levels.