Gonadotrophin-releasing hormone agonist (GnRH-a) has been widely used in the pituitary down-regulation. There are two forms of GnRH-a, long- and short-acting. These two types of GnRH-a show comparable clinical efficacy? With good acceptability and patient compliance but risk of over suppression of ovary for long-acting form, while disadvantages in acceptability and patient compliance for short-acting form. There are several protocols for down-regulation in clinical application, including long, super-long, short and super-short protocols, with different advantages and disadvantages. In general, the individualized protocol is the best one. As the identification of down-regulation is controversial, the timing of initiation of gonadotropin administration is different in different reproductive center or in different studies, which is largely dependent on the down-regulation protocols used and patient characteristics. In some existing evidence, delayed initiation showed no detrimental effects on the treatment outcomes, but may improve the quality of retrieved oocytes and endometrial receptibility, resulting in a higher pregnancy rate. In addition, the properly delayed initiation of gonadotropin administration could reduce the ampules of gonadotropin used, offering an economic benefit for the patients.%促性腺激素释放激素激动剂(GnRH-a)已经广泛地应用于体外受精(IVF)垂体降调节中.GnRH-a分长效和短效两种剂型,长效剂型患者接受性和依从性高,但有卵巢过度抑制倾向,会造成促性腺激素(Gn)用量增加、使用时间延长,因而增加经济负担,而短效者可接受性和依从性较差.两者临床效果无显著差异.临床上常用的GnRH-a降调节方案有长、超长、短、超短等方案,各种方案的临床效果总体上并无显著差异但各有优缺点,通常卵巢功能减退的患者建议给予短方案,甚至超短方案,而卵巢储备功能正常患者常用长方案.超长方案对于合并子宫内膜异位症或多囊卵巢综合征患者等能提高临床妊娠率.降调标准存在争议,因此文献报道对于Gn的启动时间亦有不同,需要根据患者个体及不同的降调节方案而定.适当延迟启动时间可能改善卵母细胞的质量和内膜接受性,从而提高临床妊娠率,而且适当推迟Gn启动时间对于减少Gn的用量,降低患者的经济负担也是十分有益的.
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