Recurrent pregnancy loss (RPL) is defined by two or more failed pregnancies and accounts for only 1-5% of pregnancy failures. Treatment options for unexplained RPL (uRPL) are limited. Previous studies suggest a link between delayed implantation and pregnancy loss. Based on this, a timely signal for rescue of the corpus luteum (CL) using human chorionic gonadotrophin (HCG) could improve outcomes in women with uRPL. This retrospective cohort study included 98 subjects with uRPL: 45 underwent 135 monitored cycles without HCG support; and 53 underwent 142 cycles with a single mid-luteal HCG injection. Based on Log-rank Mantel-Cox survival curves, miscarriage rate and time to pregnancy decreased in the HCG group (P = 0.0005). Women receiving luteal HCG support had an increased chance of an ongoing pregnancy compared with those not receiving it (RR = 2.4; 95% CI 1.4-3.6; number need to treat (NNT) = 7; 95% CI 4-18). Subjects receiving HCG support had a significant absolute risk reduction (ARR) of miscarriage (P < 0.001; ARR = 11.5%; 95% CI 3.6-19.5; NNT = 9(5-27). These data suggest restoration of synchrony and CL support improves outcomes in women with RPL. Further randomized controlled trials of luteal-phase HCG in women with RPL appears warranted.

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