The importance of endometrial pattern and thickness to successful outcome in IVF and gamete intrafallopian transfer was first described by Smith et al. (1). They found that implantation did not occur, or occurred less often, if the endometrium lacked a triple-line pattern on the day of, or one day before, ovum retrieval in IVF cycles. This finding was later confirmed by others (2, 3). A triple-line endometrial pattern on the day of hCG administration in IVF cycles is relate to serum estradiol level, the number of mature oocytes, and the number of top-quality embryos and is unrelated to serum progesterone levels (3).

　　Smith等人较先描述了子宫内膜形态和厚度对试管和配子输卵管内移植成功与否有重要作用(1)。他们发现，如果子宫内膜在试管周期试管当天或前一天没有形成三线型形态，胚胎移植后就不会着床或者着床率低，后来其它研究也证实了这一发现(2，3)。试管周期hCG给药当天形成的三线型内膜形态与血清雌二醇水平，成熟卵泡个数和专业胚胎个数相关，而与血清孕酮水平无关(3)。

　　Endometrial thickness

　　子宫内膜厚度

　　Pregcy does not occur in IVF cycles, presumably because of failure of embryos to implant, if the endometrium is too thin on the day of hCG administration according to the majority of studies. However, other studies have reported no relationship between thickness and pregcy in IVF cycles. Many of the studies that failed to find a relationship between thickness and outcome compared mean thickness in conception and non-conception cycles, while most studies that found a relationship reported critical or “cut-off” values below which no pregcies occurred. In most studies, the critical thickness value is reported as 6mm, but the range is from 4mm (4) to 6mm (5). One reason for these differences is that endometrial thickness can change, either increasing or decreasing, between the day hCG is administered and the day implantation is presumed to occur, a difference of 8-9 days. Importantly, in all studies of oocyte donation, endometrial thickness on the day of embryo transfer has been found to be critical for implantation.

　　根据大多数研究结果，如果子宫内膜在hCG给药当天太薄，胚胎可能无法着床，导致没有怀孕。但是，也有其他研究发现试管周期中子宫内膜厚度大小与是否怀孕之间没有关系。许多研究通过对比受孕和非受孕周期的内膜平均厚度得出内膜厚度与怀孕不相关的结论，而大多发现这二者之间有关系的研究则认为内膜有一个临界值，当内膜厚度低于该值时怀孕不会发生。多数研究认为内膜厚度的临界值为6mm，但是总的范围在4-6mm之间(4，5)。造成这些差异的一个原因是子宫内膜厚度在hCG给药当天和预计移植当天不同，中间相隔8-9天，内膜厚度可能增加也可能减少。研究人员还有一个很重要的发现，即在所有试管周期中，胚胎移植当天的子宫内膜厚度对移植着床至关重要。

　　As is true for ovarian induction and intrauterine insemination, optimal ART pregcy and birth rates occur when endometrial thickness on the day of hCG administration is equal to or greater than 9mm (3) or 10mm (6). Endometrium that is too thick, 14mm or greater on the day of hCG administration, may reduce the chance of a clinical pregcy (3). Increased susceptibility to injury at the time of embryo transfer has been proposed as the reason for decreased clinical pregcies by Dickey et al., who found that biochemical pregcies were more frequent in IVF cycles when endometrial thickness was less than 9mm or greater than 13mm (3). No relationship between endometrial thickness on the day of hCG and biochemical pregcy was observed in IVF cycles in another study (7). An excessively thick endometrium may have its origins in the previous cycles. It is common practice not to start ovulation induction in ART and intrauterine insemination cycles following menstruation when endometrial thickness is greater than 6mm.

　　与卵巢诱导排卵和宫腔内人工授精类似，当内膜厚度在hCG给药当天大于或等于9mm (3)或者10mm(6)时，辅助生殖周期会出现较优的妊娠率和出生率。内膜过厚，厚度大于或等于14mm时可能会降低临床妊娠率(3)。Dickey等人提出在胚胎移植时内膜对损伤的敏感性增加是临床妊娠率降低的原因，他们发现当内膜厚度小于9mm或者大于13mm时，试管周期更容易出现生化妊娠(3)。另一项研究发现试管周期中hCG给药当天内膜厚度与生化妊娠没有关系(7)。过厚的子宫内膜可能来源于上一次周期。当子宫内膜厚度大于6mm时，通常做法是不开始卵巢诱导排卵或宫腔内人工授精周期。

　　Other ultrasound findings

　　其它超声发现

　　Implantation rarely occurs when endometrial fluid is present on ultrasound on the day of embryo transfer, even when the fluid is aspirated (8). Endometrial polyps less than 2cm do not decrease pregcy rates, but there is a trend toward increased pregcy loss (9).

　　如果在胚移植当天宫腔内出现积液，即使将积液抽取出来，胚胎也很难着床(8)。小于2cm的内膜息肉不会降低妊娠率，但有增加流产的趋势(9)。

　　References

　　参考文献

　　1. Smith B, Porter R, Ahuja K, Craft I. Ultrasonic assessment of endometrial changes in stimulated cycles in an in vitro fertilization and embryo transfer program. J IVF-ET 1984; 1:233-8.

　　2. Gonen Y, Casper RF, Jacobson W, Blankier J. Endometrial thickness and growth during ovarian stimulation: a possible predictor of implantation in in vitro fertilization. Fertil Steril 1989; 52: 446-50.

　　3. Dickey RP, Olar TT, Curole DN, Taylor SN, Rye PH. Endometrial pattern and thickness associated with pregcy outcome after assisted reproduction technologies. Hum Reprod 1992; 7: 418-21.

　　4. Sundstrom P. Establishment of a successful pregcy following in-vitro fertilization with an endometrial thickness of no more than 4mm. Hum Reprod 1998; 13: 1550-2.

　　5. Shoham Z, De Carlo C, Patel A, Conway GS, Jacobs HS. Is it possible to run a successful ovulation induction program based solely on ultrasound monitoring? The importance of endometrial measurements. Fertil Steril 1991; 56: 836-41.

　　6. Check JH, Nowroozi K, Choe J, Lurie D, Dietterich C. The effect of endometrial thickness and echo pattern on in vitro fertilization outcome in donor oocyte-embryo transfer cycle. Fertil Steril 1993; 59: 72-5.

　　7. Krampl E, Feichtinger W. Endometrial thickness and echo patterns. Hum Reprod 1993; 8: 1339.

　　8. Mansour RT, Aboulghar MA, Serour GI, Riad R. Fluid accumulation o the uterine cavity before transfer: a possible hindrance for implantation. J IVF-ET 1991; 8: 157-9.

　　9. Lass A, Williams G, Abusheikha N, Brinsden P. The effect of endometrial polyps on outcomes of in vitro fertilization cycles. J Assist Reprod Genet 1999; 16: 410-15.