宫外妊娠：胚胎移植的“错误方式”

　　Embryos which are deposited in the uterine cavity “the wrong way” (coming from below rather than from above) leads to a truly un-physiological way of generating a pregnancy.

　　以“错误方式”(由下至上而非由上至下)将胚胎放置进子宫腔内实际上是一种非生理性的妊娠方式。

　　“The wrong way” relates to the fact that embryos do not descend from the tube downstream into the uterine cavity, but rather ascend through the cervix. This is the consequence of the embryos being injected, where several determinants are important. These are as follows.

　　在这种“错误方式”下，胚胎没有经输卵管下游下降至宫腔内，而是经宫颈将胚胎上移至宫腔内。这是胚胎移植的结果，与以下几个决定性因素相关。

　　1.The distance from the uterine fundas

　　离宫底距离

　　There seems to be an international understanding that the embryos should be deposited relatively close (0.5-1cm) to the uterine fundus. This seems to be best achieved using ultrasound-guided embryo transfer, provided the endometrium can be well visualized.

　　一般认为，胚胎放置的位置应该离子宫底相对较近(0.5-1cm)。超声波引导的胚胎移植似乎可以实现这一要求，前提是超声波可以很好地观察到子宫内膜。

　　In the best of cases, the catheter can be followed right up along its whole trajectory and should be positioned to just below the fundal endometrial lining (1). If this is not taken into account, the risk exists that the embryos are placed into or very near the tube itself, or may be aspirated into it by capillary suction induced by minor uterine contractions. What really happens to the embryo after being expelled from the catheter remains largely unpredictable, the embryo being very small in weight and size and hence subject to all kinds of microscopic rheological and mechanical forces.

　　在最理想的情况下，导管可以沿着超声波的整个轨迹向上移入，并且最后应该定位在子宫内膜底部的正下方(1)。如果在移植时未考虑到这一点，胚胎则有可能被放置于输卵管内或靠近输卵管的位置，或者可能由于轻微子宫收缩引起的毛细血管吸力被吸入输卵管内。胚胎从导管中排出之后发生的真实情况在很大程度上仍然无法预测，胚胎的质量和大小都非常小，因此它会受到各种微观流变和机械力的影响。

　　It also appears that the fundus should not be mechanically touched during embryo transfer, because this may cause increased junctional zone contractions, resulting in the embryos moving from the uterine cavity into the fallopian tubes (2).

　　也有人认为，胚胎移植过程中导管不能接触宫底，因为接触后可能会导致触碰区收缩力增加，导致胚胎从宫腔转移进输卵管内(2)。

　　2.Injecting lower or higher volumes

　　注射进更少或更多培养液

　　It has long been established that one should inject the lowest possible volume to dispense the embryos into the cavity, i.e. no more than 30μl of medium. Higher volumes carry the risk of being aspirated through capillary forces into the slender tubes, leading to ectopic implantations.

　　很早以前，人们就已经确定，在胚胎移植时注入到宫腔内的液体应当尽可能少量，即不超过30μl的培养液。注入更多液体会导致毛细血管力增加，胚胎可能会被吸入至输卵管内，造成宫外妊娠。

　　3.Injecting with lesser or stronger injection force

　　注射时用更小或更大的力

　　Although manually conducted transfer is the rule, some investigators have addressed the possibility of performing the embryo transfer using standardized pump-regulated injection of the embryo (3). These authors conceived an ingenious system in order to improve the pregnancy rate by standardizing the speed of injection of the fluid containing the embryos. It cannot be excluded that this may have a preventive effect on the incidence of extra-uterine pregnancy, although no data are available yet to prove this.

　　虽然人工移植是常规操作，但是一些研究人员设计出了一个巧妙的系统，通过一个标准化的泵调节注射装置可以将含有胚胎的液体以标准的注射速度注射进去，以提高妊娠率。不能排除它可能对宫外妊娠有预防作用，不过尚无研究数据证实。

　　References

　　参考文献

　　1. Tiras B, Polat M, Korucuoglu U, Zeyneloglu H B, Yarali H. Impact of embryo replacement of depth on in vitro fertilization and embryo transfer outcomes. Fertil Steril 2010;94:1341-1345.

　　2. Biervliet F P, Lesny P, Maguiness, Killick S R. Mechanisms for bilateral extopics after embryo transfer? Fertil Steril 2001;76:212-213.

　　3. Groeneveld E, De Leeuw B, Vergouw C G, et al. Standardization of catheter load speed during embryo transfer: comparison of manual and pump-regulated embryo transfer. Reprod Biomed Online 2012;24:163-169.

　　4. Lesny P, Killick S R. The junctional zone of the uterus and its contractions. Br J Obstet Gynecol 2004;111:1182-1189.