The use of natural LH surge and hCG trigger in intrauterine insemination was compared too. A meta-analysis revealed a significantly higher clinical pregnancy rate in IUI cycles with natural LH surge than that with hCG trigger. However, the data from randomized controlled trial showed no significant difference. Also the data were contradictory when the analysis confined to a specific indication of subfertility (Kosmas et al., 2007). A cochrane review in 2012 also suggested there was no evidence to advise that any regimen was better than another (Cantineau et al., 2012).