The aim of the present prospective randomized controlled study was to determine the effects of GnRHa add up to routine luteal phase support on frozen embryo implantation in frozen embryo transfer (FET).

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.

Currently, available data suggest that inadvertent administration of a GnRH agonist during a conception cycle is not accompanied by an increased risk of birth defects. On the basis of the currently strong available evidence, it appears that GnRH agonist supplementation during luteal phase significantly improve the outcome of ART treatment. Most of the former researches focused only on fresh embryo transfer in IVF/ICSI cycles. In one prospective controlled study, a single dose of Triptorelin 0.1mg was administrated 6 days after ICSI in oocyte donor cycles and the implantation rate was improved significantly.GnRH agonist administration at the time of implantation enhances embryo developmental potential, probably by a direct effect on the embryo.

Inclusion Criteria:

• infertile women with frozen thawed embryo transfer after HRT endometrial preparation.
• more than 20 years old, and less than 37 years old.
• BMI less than 28kg/m2.
• more than 1 transplantable embryo after thawing.
• patients should sign the informed consent and have the willing to follow up.

Exclusion Criteria:

• uterine malformation
• diameter of intramural myoma more than 3cm
• the thickness of endometrium less than 7mm on the progesterone supportive day.