The aim of this study was to evaluate the reproductive outcome in patients receiving frozen-thawed embryo transfer before and after doubling of the vaginal progesterone gel supplementation. The study was a retrospective study performed in The Fertility Clinic, Skive Regional Hospital, Denmark. A total of 346 infertility patients with oligoamenorrhoea undergoing frozen-thawed embryo transfer after priming with oestradiol and vaginal progesterone gel were included. The vaginal progesterone dose was changed from 90mg (Crinone) once a day to twice a day and the reproductive outcome during the two periods was compared. The pregnancy rate increased significantly after doubling of the progesterone dose (26.7% (90mg) versus 38.4% (180mg); P=0.021). Moreover, the early pregnancy loss rate decreased significantly (67.4% versus 43.7%, respectively; P=0.014), which significantly increased the delivery rate (8.7% versus 20.5%, respectively; P=0.002). Doubling of the vaginal progesterone gel supplementation during frozen-thawed embryo transfer cycles decreased the early pregnancy loss rate, resulting in a significantly higher delivery rate. This study evaluated the reproductive outcome of 346 women with oligoamenorrhoea (cycle length >34 days) or amenorrhoea undergoing oestradiol and progesterone priming prior to frozen-thawed embryo transfer. Patients treated with vaginal progesterone gel (Crinone 90mg) twice daily had a lower risk of pregnancy loss (43.7%) compared with women treated once a day (67.4%). This resulted in a significantly higher delivery rate (20.5% versus 8.7%, respectively).