Weekly intramuscular progesterone for luteal phase support in women receiving oocyte donation is associated with a decreased miscarriage rate

To determine whether adding intramuscular to vaginal administration of progesterone reduces miscarriage rates compared with those of vaginal administration alone for luteal phase support in women receiving oocyte donation and to determine the best time to introduce intramuscular progesterone.Retrospective analysis of miscarriage rates in women receiving oocyte donation. Recipients underwent endometrial preparation by hormone replacement treatment. Vaginal progesterone alone or associated with intramuscular progesterone was used for luteal support.This study analysed 186 oocyte donation cycles from January 2016 to May 2018 with embryo transfer on Day 2 or 3 and vaginal progesterone administration: 106 embryo transfer cycles with vaginal progesterone alone, 29 with weekly intramuscular progesterone added once the human chorionic gonadotrophin (HCG) assay was positive, and 51 with weekly intramuscular progesterone added the evening of embryo transfer. The rates of positive HCG assays, biochemical pregnancies and clinical pregnancies did not differ between the treatment groups. The miscarriage rate was significantly lower when intramuscular progesterone began the evening of embryo transfer than with vaginal administration alone (16.7% versus 47.0%, respectively; P = 0.049 after Bonferroni correction). The live birth rate was higher when intramuscular progesterone began the evening of embryo transfer than with vaginal administration alone (37.3% versus 16.0%, respectively; P = 0.009 after Bonferroni correction).Adding intramuscular to vaginal progesterone administration appears to decrease the miscarriage rate and increase the live birth rate in oocyte donations. The initiation of intramuscular progesterone is most beneficial when it is introduced the evening of embryo transfer.