Does assisted hatching improve implantation rates after in vitro fertilization or intracytoplasmic sperm injection in all patients? A prospective randomized study

Purpose: Preliminary data from some research centers indicate that assisted hatching might be of value to increase embryo implantation rate in the human, at least in selected cases. It is not clear, however, whether this technique would be of benefit for all patients undergoing an embryo transfer. We therefore performed a prospective randomized study to evaluate the effect of assisted hatching on the implantation rate in our in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) program. Methods: In total, 120 couples undergoing an embryo transfer were randomized between two groups: in one group no assisted hatching was performed (AH-), whereas in the other group the embryos selected for transfer. were subjected to partial zona dissection (PZD) immediately prior to the transfer (AH+). Using a computer-generated minimization procedure, patients were allocated to one of the two groups according to four preselected criteria: the number of embryos transferred, the cumulative score of transferred embryos, the age of the patient, and the use of ICSI. Results: Pregnancy and implantation rates in the AH+ and AH- groups were, respectively, 42.1 versus 38.1% and 17.9 versus 17.1%. Conclusions: From our data we conclude that assisted hatching through partial zona dissection prior to embryo transfer does not improve pregnancy and embryo implantation rates in unselected patients undergoing IVF or ICSI.