Zona opening of human embryos using a non-contact UV laser for assisted hatching in patients with poor prognosis of pregnancy.

The aim of this study was to examine the safety and the efficiency of a 'non-contact' UV laser to assist hatching through zona opening of human embryos. Between January and November 1995 we performed zona drilling for assisted hatching using a new laser system (PALM UV Laser microbeam), operating in a 'non-contact' mode to create a hole in the zona pellucida of human embryos. In a randomized study, laser zona opening was applied on embryos from two groups of patients with repeated in-vitro fertilization (IVF) failures (two to four attempts): group A was composed of 107 patients who received mixed embryos (216 laser-treated and 223 not treated) and group B of 72 patients who received 218 laser-treated embryos only. Both groups were compared with a control group of 98 patients whose embryos were not laser treated (n = 407) (group C). The mean ages of all groups (38.1, 38.2 and 37.8 years respectively) and the number of IVF attempts (two to four attempts) were similar. The resulting clinical pregnancies were 39 (36.4%) in group A, 32 (44.4%) in group B and 19 (19.3%) in group C. The implantation rates/embryo were 9.3% in A, 16% in B and 5.1% in the control group. In total, 17 normal babies have been delivered (10 in group A and seven in group B). These results show that laser zona drilling increased the pregnancy and implantation rates in all the treated patients. The increase was slight but significant in patients of group A (P < 0.01 and P < 0.02), it was even higher in the patients of group B (P < 0.05).