**4.5. Vaginal vs. IM progesterone for luteal support**

Previous randomized trials [38 ,39] and a meta-analysis [18] and a Cochrane review [19] concluded that there is evidence of superiority of I.M. over vaginal progesterone for ongoing pregnancy and live birth. These studies showed that whether natural or synthetic I.M progesterone were used the results were the same : superiority of I.M. over vaginal ` progesterone For example at least two prospective randomized trials [40,41] showed that biweekly I.M. 250 mg 17-alpha hydroxyl progesterone caproate (17 –αHPC) was superior to daily 90 mg vaginal gel. However more recent randomized trials [42 ,43] and Cochrane systematic reviews found no evidence favoring vaginal vs. I.M. administration of progesterone. The last Cochrain review and meta-analysis [21] is particularly relevant because it is the most recent (2011) and it included Sixty-nine studies with a total of 16,327 women.
