Purpose To compare effectiveness of two different chemical zona thinning techniques. Method We studied 163 patients who had experienced IVF or ICSI failures in two or more cycles. Patients were assigned to one of three groups: zona intact (n=72), partial thinning (n = 59), or circumferential thinning (n =73). Before transfer, the zonae pellucidae of embryos were thinned partially or circumferentially using acidified Tyrode's solution. Results Implantation rates were 8.9% in the intact zona group, 17.6% in the partial thinning group, and 11.9% in the circumferential thinning group: respective clinical pregnancy rates were 16.7% (12/72), 32.2% (19/59), and 27.4% (20/73). Both rates were significantly higher in the partial thinning group than the intact zona group. For circumferential thinning versus zona intact groups, differences fell short of significance. Conclusions Following embryo transfer failure, partial thinning would be recommended over circumferential thinning for successful assisted hatching.

We assessed the effectiveness of assisted hatching using a 1.48-µm diode laser in human embryos, comparing zona opening and zona thinning techniques. A total of 56 day 3 embryos were assigned randomly to a zona opening group, a zona thinning group, or a control group. We then carried out assisted hatching using the OCTAX Laser Shot system (MTG Medical Technology, Altdorf, Germany) in the first two groups. In the zona opening group, the inner membrane of the zona pellucida was broken to create a full-thickness opening. In the zona thinning group, the inner membrane of the zona pellucida was not breached. After the laser procedure, embryos were cultured to the hatched blastocyst stage. Blastocyst development rates did not differ significantly between the three groups. In the zona opening group, blastocysts were significantly more likely to hatch than those in the control group ( ≤ 0.05) and no arrested hatching of blastocysts was observed. Assisted hatching using a 1.48-µm diode laser in the zona opening technique increases the likelihood of blastocyst hatching in human embryos and does not adversely effect subsequent embryo development. (Reprod Med Biol 2006;: 221-226).

Few cases have been reported in which the aspiration of a single follicle led to the recovery of two conjoined oocytes surrounded by a single zona pellucida. This report describes a successful embryo transfer with subsequent live birth derived from conjoined oocytes, and a later pair of conjoined oocytes in the same patient. After oocyte retrieval from a patient with polycystic ovary syndrome, two pairs of conjoined oocytes were collected. One oocyte was fertilized using in vitro fertilization (IVF) and developed to the blastocyst stage. This blastocyst was cryopreserved and later transferred to the uterus after separating the unfertilized conjoined oocyte. A successful pregnancy and healthy live birth was achieved. Two years later, the patient returned for a second IVF; one pair of conjoined oocytes was detected. One of the pair was fertilized and developed to a blastocyst, but was not transferred. We demonstrate that selective fertilization of a mature oocyte from conjoined oocytes by IVF can lead to the development of a blastocyst and subsequent pregnancy and live birth. To our knowledge, this is the second case report of successful live birth from conjoined oocytes. It may be the first case of repeated fertile conjoined oocytes from the same patient.

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