Roberts C J
J Reprod Fertil Suppl. 1982;32:447-9.
Manual crushing of one blastocyst performed on 181 bicornuate twin pregnancies between Days 24 and 45 has shown that the uncrushed blastocyst can either survive and develop normally to full term or may be rejected and resorbed like its crushed twin, depending mainly on the stage of pregnancy. Crushing, which causes rupture of fetal membranes, results in a rapid fall in the survival rate of the uncrushed blastocyst when performed after Day 31. In some mares rupture is not possible after Day 35 even if extreme pressure is used. Crushed, but unruptured, blastocysts mainly between Days 35 and 45 may (a) resorb as does the uncrushed twin (60%) (b) resorb without loss of the uncrushed twin (20%) or (c) survive, as does the uncrushed twin, even when several attempts on alternate days are made to destroy the blastocyst (20%). At no stage of pregnancy is the uncrushed embryo resorbed unless the crushed twin is destroyed. The rejection and resorption of the uncrushed twin is not due to transference of pressure, but presumably to physiological processes involving prostaglandin. Mefenamic acid appears to increase survival rates especially when crushing is performed after 31 days, although the twin of apparently successful crushings at this stage may be lost between Days 50 and 70.
对181例双角子宫双胎妊娠在第24至45天进行的单个体外受精胚胎手动挤压实验表明，未挤压的胚胎要么能存活并正常发育至足月，要么可能像其被挤压的双胎一样被排斥和吸收，这主要取决于妊娠阶段。挤压会导致胎膜破裂，在第31天后进行挤压时，未挤压胚胎的存活率会迅速下降。在某些母马中，即使施加极大压力，在第35天后也无法实现胎膜破裂。主要在第35至45天之间被挤压但未破裂的胚胎可能（a）像未挤压的双胎一样被吸收（60%）（b）在未挤压双胎未丢失的情况下被吸收（20%），或者（c）即使在连续几天多次尝试破坏胚胎的情况下，仍能像未挤压的双胎一样存活（20%）。在妊娠的任何阶段，除非被挤压的双胎被破坏，否则未挤压的胚胎不会被吸收。未挤压双胎的排斥和吸收并非由于压力传递，而是可能涉及前列腺素的生理过程。甲芬那酸似乎能提高存活率，尤其是在第31天后进行挤压时，尽管在此阶段看似成功挤压的双胎可能在第50至70天之间丢失。
