Impact of assisted hatching on ART outcome in women with endometriosis. Does assisted hatching improve implantation rates after in vitro fertilization or intracytoplasmic sperm injection in all patients? A prospective randomized study. Chemical removal of the outside of the zona pellucida of day 3 human embryos has no impact on implantation rate. Enhancement of outcome from intracytoplasmic sperm injection: does co-culture or assisted hatching improve implantation rates? A randomized double-blind controlled study of the efficacy of laser-assisted hatching on implantation and pregnancy rates of frozen-thawed embryo transfer at the cleavage stage. Is assisted hatching beneficial in patients with recurrent implantation failures? Implantation enhancement by selective assisted hatching using zona drilling of human embryos with poor prognosis. Assisted hatching by partial zona dissection of human pre-embryos in patients with recurrent implantation failure after in vitro fertilization. A prospective, randomized, double-blind study for the evaluation of assisted hatching in patients with advanced maternal age. Implantation failures: success of assisted hatching with quarter-laser zona thinning. Assisted hatching does not enhance IVF success in good-prognosis patients. Laser zona thinning in women aged <or=37 years: a randomized study. Zona thinning with noncontact diode laser in patients aged < or = 37 years with no previous failure of implantation: a prospective randomized study. Mechanically expanding the zona pellucida of human frozen thawed embryos: a new method of assisted hatching. A prospective, randomized, double-blinded study of assisted hatching in women younger than 38 years undergoing in vitro fertilization. Effect of laser zona thinning on vitrified-warmed embryo transfer at the cleavage stage: a prospective, randomized study. Laser assisted zona thinning technique has no beneficial effect on the ART outcomes of two different maternal age groups. Laser assisted hatching in good prognosis patients undergoing in vitro fertilization-embryo transfer: a randomized controlled trial. Laser-assisted hatching increases pregnancy and implantation rates in cryopreserved embryos that were allowed to cleave in vitro after thawing: a prospective randomized study. Impact of assisted hatching on fresh and frozen-thawed embryo transfer cycles: a prospective, randomized study. Comparison of zona manipulated and zona intact blastocyst transfers: a prospective randomized trial. A European multicentre prospective randomized study to assess the use of assisted hatching with a diode laser and the benefit of an immunosuppressive/antibiotic treatment in different patient populations.
Assisted hatching can improve the implantation rate in cycles with poor outcome. The impact of assisted hatching in embryos from women with endometriosis is not known. Therefore, the hypothesis that the implantation potential of embryos obtained from women with endometriosis can be improved with assisted hatching was tested.
                In a prospective randomized study, transfer embryos obtained from 60 women with endometriosis were hatched using a laser system and compared to embryos obtained from patients with the same diagnosis which were left intact (n = 30).
                The characteristics of cycles were similar between groups. The pregnancy (40% zona intact, 28.3% assisted hatching), and implantation rates (19.4% zona intact, 17.8% assisted hatching) did not differ in endometriosis cycles regardless of assisted hatching.
                Assisted hatching does not improve outcome in women with endometriosis undergoing assisted reproduction. 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.
                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 pre-selected criteria: the number of embryos transferred, the cumulative score of transferred embryos, the age of the patient, and the use of ICSI.
                Pregnancy and implantation rates in the AH+ and AH- groups were, respectively, 42.1 versus 38.1% and 17.9 versus 17.1%.
                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. Two hundred eighteen consenting patients entered a randomized study of the application of chemical zona pellucida thinning on their day 3 embryos, prior to uterine transfer. Of those control patients (n = 108), whose embryos remained unmanipulated, 40 (37.0%) have ongoing/delivered pregnancies, while in the experimental group (n = 110), whose embryos had their zonae pellucidae chemically thinned, there are 49 patients (44.6%) who have ongoing/delivered pregnancies. Although this difference is not significant, clearly the application of this micromanipulative intervention has not been detrimental, and this bodes well for routine application of embryonic micromanipulation procedures in general. Certain patient subgroups were studied including older women, those with elevated basal follicle stimulating hormone levels, patients with embryos of differing zona thickness, and patients with embryos of differing uniformity of zona thickness. No significant influence of chemical removal of the outside of the zona on the implantation rate of embryos in any of these subgroups was observed other than a marginally significant (P = 0.095) improvement of implantation of embryos with less than 4.0 microns variation in zona thickness when chemical zona thinning was applied. Failure of chemical zona thinning to enhance human embryo implantation significantly, compared to assisted hatching by complete zona drilling, strongly suggests that the bilayered human zona pellucida needs to be fully breached, unlike that of the mouse. In two separate prospectively randomized trials, intracytoplasmic sperm injection (ICSI) cycles were studied in a controlled manner to monitor the effects of either bovine oviductal epithelial cell co-culture (n = 119) or assisted hatching by zona drilling (n = 100). In the first study, immediately following ICSI, all eggs were placed directly either onto partial monolayers of bovine oviductal cells or into regular culture medium. Although the embryo developmental rate was apparently compromised in part by the presence of the co-culture cells, ultimately there were no significant differences in either the viable pregnancy rate (31.6% co-culture versus 29.0% control) or the embryonic implantation rate (11.4% co-culture versus 13.6% control). Assisted hatching also had no significant impact on ICSI cycle outcome in terms of either the viable pregnancy rate (30.0% assisted hatching versus 32.0% control) or the embryonic implantation rate (8.5% assisted hatching versus 13.5% control). However, in female patients aged > or = 35 years, assisted hatching appeared to convey a marginally significant benefit in terms of both the viable pregnancy rate (35.5% assisted hatching versus 11.1% control) and the embryonic implantation rate (10.3% assisted hatching versus 3.1% control). It seems that the overall improvement of ICSI cycle outcome cannot be achieved by the general application of either co-culture or assisted hatching. Nevertheless, it is possible that there remain specific patient groups that might benefit from selected use of either of these modalities. Assisted hatching (AH) in fresh embryo transfer (ET) cycles increases the implantation and pregnancy rates, especially in women with a poor prognosis, repeated implantation failures and in older women. Little information exists in the literature regarding the role of AH in frozen-thawed embryo transfer (FET) cycles.
                Embryos were cryopreserved at the cleavage stage. On the day of FET, 160 patients were randomized according to a computer-generated randomization list in sealed envelopes into the AH group and the control group. The patients and the clinicians were blinded to the group assigned. In the AH group, the outer half of the zona pellucida over a quarter of the diameter of zona was removed using a 1480 nm non-contact laser.
                The two groups were comparable in terms of demographic characteristics, ovarian response of the stimulated cycle and quality of fresh and frozen-thawed embryos. No differences in implantation, pregnancy and multiple pregnancy rates were found between the two groups. There was a non-significant trend of a higher implantation rate in the AH group when the zona thickness was > or = 16 mm.
                Laser AH did not improve the implantation rate of FET cycles and should not be performed routinely in all frozen-thawed embryos at the cleavage stage. To assess the possible role of assisted hatching in patients with recurrent implantation failure during IVF cycles.
                Prospective randomized study.
                IVF unit of an academic medical center.
                Women who underwent IVF after at least three failed IVF-ET attempts.
                Patients were prospectively randomized to undergo assisted hatching of their embryos prior to their replacement by mechanical partial zona dissection.
                The study (assisted hatching) and control groups included 104 and 103 patients, respectively. There were no significant between-group differences in patient age, cause of infertility, mean number of previous IVF trials, number of oocytes retrieved, fertilization rate, or number of embryos transferred. No difference in pregnancy rate was noted on comparison of the whole study group, to the whole control group (21% and 27%, respectively). However, when the results were re-analyzed by age groups, assisted hatching was found to be harmful in the youngest group (< 34 years), significantly decreasing pregnancy rates (15% vs 35%, p < 0.05).
                Repeated implantation failure alone is not an indication for assisted hatching. Although assisted hatching appears to be effective in a selected group of older patients, in younger patients it may further hamper implantation and should be avoided. Assisted hatching by zona drilling using acidic Tyrode's solution was performed during three randomized trials in 330 in-vitro fertilization patients. The trials were designed in order to study the overall effect of the procedure and whether characteristic patient [i.e. maternal age and basal levels of follicle stimulating hormone (FSH)] and embryonic features (i.e. zona pellucida thickness) are important for the decision to perform assisted hatching routinely. Couples (n = 137; Trial 1) in whom the female partner had normal basal FSH levels were randomized in a control group (without micromanipulation) and a zona drilling group (all embryos micromanipulated). The incidence of implantation (67/239; 28%) of zona-drilled embryos compared favourably with that of control embryos (49/229; 21%), but the difference was not significant. Retrospective analysis revealed that those embryos whose zonae were thicker than 15 microns were rescued. In order to test the validity of this finding, selective assisted hatching was performed on embryos with a poor prognosis in 163 other patients (Trial 2). The couples were randomized into a control group and a group in which embryos were selectively zona-drilled, based on zona thickness and other embryonic features. The rate of embryonic implantation in the selectively zona-drilled group was 25% (70/278), significantly (P less than 0.05) higher than that of control embryos (51/285; 18%). Although it was demonstrated retrospectively and prospectively that assisted hatching by zona drilling is effective in embryos with thick zonae (greater than or equal to 15 microns), patients whose embryos have thin (less than 13 microns) zonae may be jeopardized by the procedure.(ABSTRACT TRUNCATED AT 250 WORDS) To examine the potential of the partial zona dissection technique to promote successful implantation by assisting embryo hatching after IVF.
                The study and the control group included 72 and 82 patients, respectively, each had undergone at least three failed IVF-ET attempts. Assisted hatching was performed on four- to six-cell stage embryos by creating a slit in the zona pellucida using the partial zona dissection technique. After 90 minutes incubation (5% CO2, 37 degrees C), the embryos were transferred to the uterus.
                Infertility and IVF Unit of an academic tertiary referral medical center.
                In the assisted hatching group, 230 micromanipulated embryos were replaced (3 or 4 treated embryos per patient) compared with 295 nonmanipulated embryos in the control group. Clinical pregnancy rates (PRs) were similar in the assisted hatching and control groups (n = 15; 20.8% and n = 12; 14.6%, respectively). However, the contribution of assisted hatching by partial zona dissection to successful implantation was related to the patients's age: patients older than 38 years showed a markedly higher PR after assisted hatching: 23.9% in the study group compared with only 7% of the controls.
                These results demonstrate that assisted hatching by partial zona dissection is a quick and efficient method that does not induce any visible damage to the embryos replaced. In a selected group of patients (aged over 38 years, who have failed to conceive in at least three previous IVF attempts) it significantly increases the chances for pregnancy after ET. The objective of this study was to determine if assisted hatching improved the rates of implantation, clinical pregnancy and ongoing pregnancy for in-vitro fertilization (IVF) patients aged > or =36 years. On the day of oocyte aspiration, consenting patients were randomized according to whether all embryos underwent the hatching procedure (hatched; n = 41) or all embryos remained unhatched (controls; n = 48). Patients in both groups were treated with methylprednisolone and doxycycline starting on the day of oocyte retrieval and continuing for 4 days. The hatching procedure was performed approximately 55 h after insemination on all potential embryos for transfer and employed the release of acidified acid Tyrode's medium against the zona pellucida to create an opening approximately 20 microm in diameter. No significant differences were noted in the mean age, number of oocytes aspirated and number of embryos transferred between the hatched and control groups. In addition, no significant differences were observed in the rates of implantation (11.1 versus 11.3%), clinical pregnancy (39.0 versus 41.7%) and ongoing pregnancy (29.3 versus 35.4%) between the hatched and control groups respectively. These results suggest that assisted hatching may have no significant impact on IVF success rates in the patient population studied. Implantation failure after IVF is one of the factors associated with a reduced chance of pregnancy for some patients. Assisted hatching methodologies are designed to facilitate the embryo's escape from the zona pellucida, and this strategy has been suggested as a means of improving pregnancy rates in patients with previous implantation failure. The aim of this prospective and randomized study was to evaluate the efficacy of quarter-laser zona thinning assisted hatching (qLZT-AH) in improving the implantation of embryos in patients with previous implantation failure. A total of 150 patients with a history of previous implantation failure were treated with intracytoplasmic sperm injection, and allocated into two groups: group 1, only one previous implantation failure, and group 2, repeated implantation failures. The patients in each group were randomized at the time of embryo transfer into a control group (no qLZT-AH) or experimental group where qLZT-AH was performed. For patients with repeated implantation failures, the implantation rate in those who received laser-thinned embryos was significantly higher (P = 0.02) than in those whose embryos were not laser-thinned (10.9 and 2.6% respectively). However, this difference was not observed in patients who presented with only one previous implantation failure. The data demonstrate that qLZT-AH is an effective strategy for improving the implantation of embryos in patients with repeated implantation failures. The role of assisted hatching in good-prognosis IVF patients was evaluated in a prospective, randomized, controlled pilot study, which was followed by a retrospective observational series.
                After assisted hatching was proved successful in a mouse embryo study, 20 good-prognosis IVF patients were randomly assigned to either assisted hatching (13) or no assisted hatching (7; the controls). Following this series, 27 good-prognosis IVF patients were retrospectively evaluated to determine the outcome with assisted hatching.
                In the prospective study, clinical pregnancies resulted from 3 (23%) of 13 patients in the hatching group, compared to 3 (43%) of 7 in the control group. Implantation rates were similar: 9.6% in the hatching group and 10.7% in the controls. In the retrospective series, the 11.1% implantation rate with assisted hatching was significantly less than the 42.9% implantation rate seen with traditional IVF.
                Implantation and pregnancy rates are high in young women undergoing traditional IVF. Assisted hatching is not beneficial in these patients. The objective of this prospective randomized double-blind clinical trial was to evaluate whether laser zona pellucida thinning of human embryos improves clinical outcomes in women <or=37 years old undergoing IVF-ET treatment. The study did not reveal any significant beneficial effect of laser zona thinning on clinical pregnancy (16 out of 45 vs. 18 out of 39) and live birth rates (13 out of 45 vs. 16 out of 39) between the laser-treated and nontreated groups of patients, although there was a trend toward an increased incidence of dichorionic multiple pregnancies in the study group compared with the control group (7 out of 13 vs. 4 out of 16). Zona thinning (ZT) is a technique used to improve pregnancy rates among patients > or = 38 years old and/or patients presenting previous implantation failure. The objective of the study was to determine whether ZT has a beneficial effect on patients younger than 37 years who are undergoing the first ICSI attempt.
                A total of 103 patients submitted to ICSI for the first time and those aged < or = 37 years were divided in a prospective and randomized manner into two groups: group I, patients submitted to ZT (n = 51) (a laser diode with 1.48-micron wavelength (Fertilaser) was used for the procedure); group II, patients with no ZT (n = 52). In both groups, embryo transfer was performed on the second day.
                The age of group I patients (31.8 +/- 3.6) did not differ (P = 0.53) from that of group II patients (31.4 +/- 3.6). The number of metaphase II oocytes was similar (P = 0.76) for the two groups (group I = 9.12 +/- 5.27; group II = 8.67 +/- 5.02). The average number of embryos available per transfer of group I (6.14 +/- 4.02) did not differ (P = 0.69) from that of group II (5.75 +/- 3.83). The number of embryos transferred was similar (P = 0.61) for the two groups (group I = 2.76 +/- 0.9; group II = 2.87 +/- 0.79). The thickness of the zona pellucida of group I embryos (16.6 +/- 2.2 microns) did not differ (P = 0.08) from that of group II embryos (17.1 +/- 1.7 microns). The rate of embryo implantation (20.8%) and the rate of clinical pregnancy per embryo transfer (40.3%) were higher for group II than for group I (17.7% and 33.3%, respectively), but the difference was not significant (P = 0.55 and P = 0.54).
                These results suggest that ZT in the population aged < or = 37 years and with no previous failure of implantation may have no impact on intracytoplasmic sperm injection success rates. To determine whether a new assisted hatching (AH) method increases the implantation and clinical pregnancy rates of frozen-thawed day-3 (D3) embryos.
                Prospective study.
                A university hospital in vitro fertilization (IVF) program.
                Patients who had their first IVF/intracytoplasmic sperm injection (ICSI) cycles between June 1, 2006, and December 31, 2008, with fresh IVF-embryo transfer failures or without fresh embryo transfer.
                The couples were randomized into thawed embryo transfer after AH versus no AH. In the AH group, the zona pellucida (ZP) of D3 frozen-thawed embryos was expanded by injected hydrostatic pressure after thawing. In the control group, embryos were pierced by ICSI needles without expanding the ZP.
                Clinical pregnancy and implantation rates.
                The morphologic features of the blastomeres were carefully monitored and recorded. In the AH group, 244 embryos were thawed, and 178 (73.0%) survived; in the control group, 259 embryos were thawed, and 190 (73.4%) survived. Despite the transfer of a similar number of embryos, the AH group resulted in statistically significantly higher implantation and clinical pregnancy rates compared with the no AH group.
                Mechanically expanding the ZP of frozen-thawed D3 embryos with injected hydrostatic pressure after thawing increases the implantation rate compared with control embryos.
                Copyright (c) 2010 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved. To determine whether assisted hatching is beneficial to IVF patients younger than 38 years whose embryos have a thickened zona pellucida (ZP).
                Prospective, randomized, double-blinded, crossover study.
                University-based infertility center.
                One hundred twenty-one women less than 38 years of age, undergoing IVF at Washington University between April 2004 and February 2007, with ZP thickness > or =13 microm for any embryos.
                Measurement of ZP thickness in embryos undergoing IVF; randomization of women with embryos with ZP thickness > or =13 microm to no procedure or assisted hatching performed by acidic Tyrode's solution.
                Clinical intrauterine pregnancy rate, implantation rate, spontaneous pregnancy loss, and live birth rate.
                Baseline characteristics and ZP thickness were not significantly different between the two study arms (hatched and unhatched). No significant differences were observed between hatched and unhatched patients in the rates of clinical pregnancy (47% vs. 50% respectively) or live birth (46% vs. 45% respectively). Further, no significant differences were noted between hatched and unhatched groups in rates of spontaneous abortions, monozygotic twinning, dizygotic twinning, chromosomal abnormalities, or ectopic gestations. In addition, mean ZP thickness did not have a significant effect on pregnancy.
                In patients younger than 38 years with embryos with ZP thickness of > or =13 microm, assisted hatching does not improve the rates of implantation, clinical pregnancy, or live birth, and thus does not appear to offer any benefit to patients in this age group undergoing IVF.
                Copyright 2010 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved. The aim of this study was to determine if laser zona thinning could improve the rates of pregnancy and implantation for vitrified-warmed embryo transfer at the cleavage stage. A total of 400 vitrified-warmed embryo transfer cycles were randomly assigned to either the test group or the control group. The zona pellucida of vitrified-warmed embryos in the patients of the control group was untreated, whereas in the test group it was partially thinned by laser just before embryo transfer. In the test group, the clinical pregnancy and implantation rates were significantly lower as compared with that of the control group (28.5 versus 43.0, P=0.002, and 11.2 versus 16.7, P=0.004, respectively). Therefore the results of this investigation show that laser zona thinning may have an unexpected adverse effect on the rates of clinical pregnancy and implantation of vitrified-warmed embryos at the cleavage stage.
                2009 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved. Laser assisted zona thinning is a technique used for facilitating embryo's hatching process and is commonly used for the embryos of poor prognosis patients with advanced maternal age, repeated implantation failures, poor embryo quality or thick zona pellucida. The aim of this study was to investigate the effect of zona thinning on both good or poor prognosis patients of two different age groups.
                We investigated two different age groups (group 1: <35 years and group 2: ≥35 years ) and compared the effect of assisted zona thinning (groups 1A and 2A) versus not-thinned controls (groups 1B and 2B) in both groups.
                The clinical pregnancy rates were 57% and 56% in groups 1A and 1B (p = 0.86), 43% and 38% in groups 2A and 2B (p = 0.59) respectively.
                Our results suggest that laser assisted zona thinning of day 3 embryos has no beneficial effect on clinical pregnancy and implantation outcomes. To evaluate whether assisted hatching improves clinical outcomes of embryo transfers to good prognosis patients, defined as patients < or =39 years with normal follicle-stimulating hormone (FSH) and E(2) levels, no more than one previous unsuccessful cycle of in vitro fertilization (IVF)-embryo transfer, and good embryo quality.
                Prospective randomized controlled trial.
                Private assisted reproductive technology (ART) center.
                One hundred ninety-nine good prognosis patients undergoing IVF-embryo transfer.
                In vitro fertilization followed by embryo transfer on day 3 after oocyte retrieval with or without assisted hatching using a 1,480-nm wavelength infrared laser.
                Clinical intrauterine pregnancy, spontaneous pregnancy loss, and live birth.
                Rates of clinical intrauterine pregnancy with fetal cardiac activity (53% vs. 54% per cycle), spontaneous pregnancy loss (13% vs. 16% per pregnancy), and live birth (47% vs. 46% per cycle) were very similar between treatment cycles with laser-assisted hatching and control cycles in which embryos were transferred without assisted hatching. There were no significant differences between treatment and control groups in any measured clinical outcome parameters.
                Assisted hatching does not improve clinical outcomes among good prognosis patients. Cryopreservation of embryos may lead to zona hardening that may compromise in vivo hatching and implantation following thawing and transfer. Assisted hatching (AH) has been advocated as a means of assisting the natural hatching process and enhancing implantation.
                The aim of this study was to assess in a prospective randomized manner the effect of laser-assisted hatching (LAH) on implantation as well as clinical and multiple pregnancy rates (the primary outcome) after the transfer of frozen-thawed embryos. All embryos were thawed the day before transfer, and LAH was performed the next day on embryos that cleaved. Control group consisted of embryos that were transferred without AH.
                The performance of LAH significantly increased implantation (9.9 versus 20.1%, P < 0.01), clinical pregnancy (27.3 versus 40.9, P < 0.05) and multiple pregnancy rates (16 versus 40.3%, P < 0.07). In the LAH group, significantly more excess embryos that were left in culture hatched in vitro.
                LAH improves the outcome of frozen-thawed embryo transfer when performed before transfer on embryos that were allowed to cleave. The aim of this study was to determine if assisted hatching (AH) could improve the rates of pregnancy and implantation for both fresh and frozen-thawed embryo transfer cycles. A total of 760 fresh embryo transfer cycles and 200 frozen-thawed embryo transfer cycles were randomly assigned to either the treatment group (AH) or the control group (no AH). Zona thinning by laser was performed just before embryo transfer. In fresh embryo transfer cycles, the AH group and control group results were comparable. There were no significant differences in the rates of positive human chorionic gonadotrophin (HCG; 47.5 versus 48.8%), clinical pregnancy (42.4 versus 42.6%), or implantation (26.3 versus 25.2%) between the two groups. However, in frozen-thawed embryo transfer cycles, the rates of positive HCG (32.0 versus 17.0%), clinical pregnancy (25.0 versus 14.0%) and implantation (16.7 versus 7.3%) were significantly greater in the AH group than in the control group (P &lt: 0.05). The results of this investigation show that in the fresh embryo transfer cycles, laser-assisted hatching by zona thinning has no impact on the rates of positive HCG, clinical pregnancy and implantation, whereas in frozen-thawed cycles, assisted hatching by zona thinning significantly increases all three of these rates. In this prospective randomized study the effects of enzymatic treatment of zona pellucida of blastocysts on implantation and pregnancy rates were evaluated in a group of patients who had more than five embryos on day 3.
                Forty-six patients with a mean age of 29.8 +/- 4.5 years and mean duration of infertility of 6.72 +/- 0.63 years had blastocyst stage transfers, with a mean number of 2.9 +/- 0.1 embryos replaced per patient. Patients were randomly divided into two groups. The first group consisted of patients (n = 22) who had zona intact blastocyst stage transfers and the second group consisted of patients (n = 24) who had zona manipulated (enzymatic treatment) blastocyst stage transfers. Patient and cycle characteristics were similar in both groups. A commercial cell and serum-free sequential culture system was used for all embryos.
                Overall blastocyst formation rate was 50.3%. Transfer could be done in all patients. The positive beta-human chorionic gonadotropin rate in the zona intact group was 50% (11/22) and in the zona-manipulated group was 70.8% (17/24). Clinical pregnancy, ongoing pregnancy, and implantation rates in zona intact and manipulated groups were 45.5%, 27.3%, and 19%, and 62.5%, 45.8%, and 24% respectively. Although implantation and pregnancy rates in the zona-manipulated group were higher, there were no statistically significant differences in terms of these variables between two groups. No triplet pregnancy was obtained in either group, and the twin pregnancy rate was 20% (2/10) in the zona intact group and 13.3% (2/15) in the zona-manipulated group.
                With further improvements in the embryo culture systems it will become possible in the near future to achieve high implantation rates even with single blastocyst transfers. Enzymatic treatment of the zona pellucida seems that it does not alter the pregnancy and implantation rates, but further studies with larger group of patients are needed to clarify the real effect of this zona manipulation on pregnancy outcome. Assisted hatching (AH) techniques, designed for facilitating the embryo escape out of the zona pellucida (ZP) have been used in IVF centres since 1992. The initial indications for AH were patient's age, ZP thickness, high basal FSH and repeated IVF failures. Several retrospective and prospective studies assessing AH in these indications have given disparate results. Our aims were to evaluate the benefits of AH and immunosuppressive/antibiotic treatment (IA) in patients with either a poor prognosis of success, previous implantation failures or transfers of cryopreserved embryos.
                Four IVF centres allocated 426 patients, randomized for AH and IA, into four groups of AH indications between 1997 and 1999. AH was performed with a diode laser. ZP thickness, opening size and embryo score were recorded. Outcome measures were implantation and delivery rates.
                Patients coming for a first or third transfer of cryopreserved embryos and poor prognosis patients admitted for a first trial did not benefit from AH. Even patients with repeated implantation failures of fresh embryos did not gain significantly from AH.
                Among AH indications, absence of implantation after several transfers of good quality embryos remains the strongest patient selection criterion. Prescription of an immunosuppressive/antibiotic treatment is essential.
This update has demonstrated that whilst assisted hatching (AH) does appear to offer a significantly increased chance of achieving a clinical pregnancy, the extent to which it may do so only just reaches statistical significance. The 'take home' baby rate was still not proven to be increased by AH. The included trials provided insufficient data to investigate the impact of AH on several important outcomes. Most trials still failed to report on live birth rates.