LAUSR

RESEARCH QUESTION Will luteal phase rescue with additional progesterone increase serum progesterone concentrations and improve reproductive outcomes in patients with low serum progesterone concentrations undergoing hormone replacement therapy (HRT) cycles? DESIGN Case-control study including 40 consecutive patients with serum progesterone concentrations <8.75 ng/ml on the 5th day of progesterone supplementation who underwent rescue with a daily bolus of 25 mg s.c. progesterone, starting on the afternoon of the 5th day of progesterone administration. For every patient who underwent progesterone rescue, three patients matched by age, body mass index, number of previous attempts and number of blastocysts transferred, with serum progesterone concentration >8.75 ng/ml on the 5th day of progesterone administration served as controls (n = 120). The main outcome measure was ongoing pregnancy rate (OPR). RESULTS Baseline demographic features and embryological data of the rescue and control groups were comparable. As expected, the mean serum progesterone concentration was lower in the rescue group on the 5th day of progesterone administration (7.84 ± 0.92 versus 15.32 ± 5.02 ng/ml; P < 0.001). Following rescue, the mean serum progesterone concentration on the day of vitrified-warmed embryo transfer (6th day of progesterone administration) was 33.43 ± 10.83 ng/ml (range 14.61-82.64 ng/ml), and the OPR of the rescue and control groups were comparable. CONCLUSIONS In patients undergoing HRT vitrified-warmed blastocyst transfer with serum progesterone concentrations lower than 8.75 ng/ml 1 day prior to the scheduled embryo transfer (6th day of progesterone administration), additional supplementation with a 25 mg s.c. daily progesterone dose seems to rescue the cycle, resulting in OPR comparable to those of patients with serum progesterone >8.75 ng/ml.