胚胎殘留於植入管後再次施行二次植入對懷孕率有不良影響‧
原因不明，可能是容易造成子宮收縮，胚胎回沖入植入管後受損，子宮內膜出血，溫度變化，子宮頸黏液...等‧

The final stage involves checking whether the embryo became stuck in the catheter after the procedure. If it happens, this allows its re-introduction into the uterine cavity; however, in such cases, our experience suggests an unfavorable prognosis

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5095273/