There have certainly been cases of women becoming pregnant and giving birth after an endometrial ablation, but these cases are rare. There have also been cases of abnormal pregnancies where the placenta has implanted too deeply in the damaged wall of the uterus and when the baby has been delivered very prematurely.
For this reason the operation should be regarded as an alternative to hysterectomy for heavy periods and most surgeons would feel happier if the woman requested sterilisation either prior to or during the procedure. It is, of course, extremely unlikely that you would conceive but this is theoretically possible and you should consider a reliable form of contraception.