GIFT is the procedure where the the eggs (usually 2-3 eggs) and specially washed sperms are placed within the ampulla or the trumpet- like end of the tube by laparoscopy while ZIFT is when 2-3 embryos are placed into the fallopian tube. GIFT is usually done on request from couples who would like the eggs to be fertilised within the fallopian tube, and not outside the body as in IVF, an extracorporeal procedure. As for ZIFT, though it is seldom carried out nowadays, as pregnancy rates are relatively good with standard IVF and ICSI, it could occasionally result in pregnancies when IVF or ICSI did not work.
Embryo transfer used to be and still is done in many IVF centres either on day 2 or day 3 (egg retrieval day is day zero) when the embryos are at the early cleavage stage. However there is a trend towards extended culture to day 5, the blastocyst stage, which would allow the more robust embryo, usually single, to be selected for transfer into the uterine cavity.
Assisted hatching is as its name implies, assisting the developing embryo or the blastocyst to break out of the shell, either manually by dissection under the microscope or as in our IVF laboratories, by using a laser beam to precisely cut a tiny hole on the embryo shell. AH is done because sometimes the embryo shell is too hard or too thick for the embryo to hatch and this can happen in laboratory-cultured embryos and in oocytes of older women.