<qa>  What is the most common way to administer GnRHa?Some recent data have suggested a beneficial effect of GnRHa administered in the luteal phase on the outcome of assisted reproduction techniques. In those studies, the dose and administration time of GnRHa are inconsistent. Single administration on third day after embryo transfer and multiple dose injection during luteal phase are the most common way. The GnRHa included Triptorelin 0.1mg, Leuprorelin 1mg and Buserelin 600ug et al. The exact underlying mechanism is still not clear, although it has been hypothesized that GnRH agonist either supports the corpus luteum function by inducing LH secretion by the pituitary gonadotrophin cells or stimulates the endometrium GnRH receptors . Tesarik et al.postulated a direct effect of GnRH agonist on the embryo, evidenced by increased β-HCG secretion. 