我都唔係太清楚, , but according to cutecutetown's description:
擴宮 (dilatation)
some patients need it because it is nearly impossible to put the embryos into their womb. It is not a compllicated procedure; and for those patients who had it done, they had easier ET. An ET carried out non-traumatically has better chance than an ET which is traumatic (which makes you very painful, due the the various special tools to straighten your cervix, transverse the cervical canal, "forcing" through into the uterus, etc.).