Subzonal insemination, partial zona dissection or intracytoplasmic sperm injection? An easy decision?

This review aims to analyse and compare the results to dateof subzonal insemination (SUZI), partial zona dissection (PZD)and intracytoplasmic sperm injection (ICSI) to evaluate criticallywhether it is now possible to replace SUZI and PZD by ICSI.It appears that ICSI is a much more efficient assisted reproductiontechnique than SUZI and PZD for resolving cases of severe maleinfertility and/or repeated failure of conventional in-vitrofertilization (IVF). For ICSI compared with SUZI and PZD, fertilization(49.4, 17.7 and 16.8% respectively), percentage of patientsreaching embryo transfer (91.0, 55.1 and 23.3% respectively),percentage of transfers performed with two or three embryos(83.3% ICSI and 39.3% SUZI), pregnancy rate per embryo replacement(28.2, 18.7 and 16.5% respectively) and pregnancy rate per oocyteretrieval (24.8, 10.3 and 3.8% respectively) are all improved.In addition, cases of severely impaired semen characteristics,which were condemned to infertility for life with conventionalIVF, SUZI or PZD, can now be treated and resolved efficientlywith ICSI.     

Micro-assisted fertilization in patients who have failed subzonal insemination

During the past 3 years we have used direct injection of spermatozoainto the cytoplasm of the oocyte (DISCO) in an attempt to procureconception in vitro where subzonal insemination (SUZI) has failed,Acknowledging the paucity of information about this invasiveprocedure in humans, it was clearly the only alternative forsome patients. A total of 58 patients (cycles) who had had previouslyfailed SUZI elected for this approach. Sibling oocytes, wherepossible, were used as a comparison between DISCO, SUZI, partialzona dissection (PZD) and microdrop in–vitro fertilization(IVF). Fertilization and embryo transfer was achieved by 66%(n = 38) of patients. Patients with embryos derived solely fromDISCO (n = 19) produced four clinical pregnancies (21%), fourpatients had embryo transfer from SUZI embryos only with nopregnancies, and 15 had embryo transfer from a mixture of SUZIand DISCO embryos, with one dizygotic twin pregnancy from acombined SUZI and DISCO embryo transfer (7%). Twins, one maleand one female, have been delivered, there has been one miscarriageand two pregnancies are ongoing. Of the 627 oocytes, 251 wereused for DISCO and 71 (28%) were fertilized, 296 were used forSUZI and 29 (10%) were fertilized; 70 were used for PZD, two(3%) were fertilized. and none of the 10 undergoing microdropIVF were fertilized. Of the 58 patients (cycles) 31% (n = 19)had fertilization with DISCO only, 8% (n = 4) with SUZI only,28% (n = 15) with both SUZI and DISCO, while only one (2%) hadfertilization with PZD. The incidence of fertilization in sampleswith <5% normal forms was higher (37%) after DISCO than SUZI(15%). Of four cases with globozoospermia one achieved fertilizationwith DISCO only, and of cight cases of 100% immotile spermatozoa,two achieved fertilization with DISCO only and one with SUZIand DISCO. We conclude from this series of patients that DISCOmay not only be an advantage when SUZI fails but may becomethe first micro–assisted fertilization approach     

两种人工辅助孵化方法在IVF-ET中的比较性研究

目的探讨两种辅助孵化方法对体外受精-胚胎移植(IVF-ET))临床结果的影响,以便选择较好方法.方法在体外受精后胚胎培养的第2d,用Protease消化和机械磨擦两种孵化方式分别对年龄超过32岁的各30例妇女的移植胚胎进行人工孵化.结果采用Protease 30例辅助孵化,妊娠11例,妊娠率36.6 %;采用机械辅助孵化30例,妊娠8例,妊娠率26.7%,两者有显著性差异(P＜0.05 ).结论 Protease孵化法与机械磨擦孵化法相比具有方法简单、操作时间短、成本低、妊娠率高,有重要应用推广价值.     

Laser zona pellucida thinning--an alternative approach to assisted hatching

BACKGROUND: The purpose of this study was to assess the efficacy and hatching characteristics of in-vitro cultured human embryos subjected to laser zona pellucida thinning. METHOD: Zona thinning was performed on 110 embryos using a non-contact 1.48 microm diode laser and the hatch rate in vitro was compared with 42 control embryos. Variation of zona thickness and degree of zona expansion was assessed. Scanning electron microscopy was performed on embryos entrapped during hatching to identify the site of hatching. RESULTS: The rate of hatching was significantly higher in laser thinned blastocysts compared with control embryos (68 versus 33% respectively, P < 0.01). Laser thinning increased the variation of zona thickness in embryos from 11.6-27.3%. Natural zona thinning occurred in 92% of laser thinned hatching blastocysts and 100% of control embryos. CONCLUSION: These results suggest that laser zona thinning is effective and may provide significant advantages over conventional assisted hatching techniques, which create holes.     

Usefulness of partial dissection of the zona pellucida in a human in-vitro fertilization programme.

The influence of partial zona dissection (PZD) on the fertilization rate was studied in 34 couples with a history of fertilization failure and/or severe sperm deficiency. Overall, PZD improved the rate of monospermic fertilization compared to controls (41/254 versus 6/111: P less than 0.001) and fertilization was achieved in 50% of cases. However, the results differed according to the seminal characteristics. In 10 couples with at least two in-vitro fertilization (IVF) trials entailing total fertilization failure and with semen defined as normal, PZD did not significantly improve the monospermic fertilization rate (6/44 in the PZD group versus 2/39 among controls). A benefit related to PZD was evident in 33 attempts with severe sperm deficiency. In this group, only four of 72 unmanipulated control oocytes were fertilized but the monospermic fertilization rate was 14.6% for PZD oocytes. The rates of polyspermy were 40% and 14.6% in the groups with normal and abnormal semen parameters respectively. Of 33 trials with defective spermatozoa, 20 reached the stage of embryo transfer and three pregnancies were obtained, of which one aborted at 9 weeks.     

IVF treatment of moderate male factor infertility: a comparison of mini-Percoll, partial zona dissection and sub-zonal sperm insertion techniques

In this study we examined various techniques of in-vitro fertilization(IVF) for treating couples in whom the male had subnormal semenparameters. We compared two sperm preparation methods (mini-Percolland conventional swim-up) for efficiency of recovery after preparationand for fertilization rates after IVF, and compared the suitabilityof partial zona dissection (PZD) and sub-zonal sperm insertion(SUZI) to patients with different types of male factor infertility.The mini-Percoll technique allowed the recovery of significantlymore motile spermatozoa from the same semen sample comparedto the swim-up method. More oocytes were fertilized after spermatozoawere prepared by the mini-Percoll technique. An increased numberof spermatozoa recovered from an ejaculate led to an improvementin the quality of spermatozoa in the insemination droplet. Subsequently,when using the PZD technique, the fertilization rate increasedwhen there was a higher number of spermatozoa in the patient'sejaculate. When comparing the two micromanipulation techniques,SUZI provided patients with oligoasthenzoo-spermia (i.e. <10 x 10⁶ spermatozoa/ml and 40% motility) with a higher chanceof obtaining 2-pronculeate eggs.     

Zona thinning with the use of laser: a new approach to assisted hatching in humans

From 1993 to 1994, in our centre, laser-assisted hatching wasperformed on 2- to 4-cell stage embryos obtained from in-vitrofertilization (TVF) patients. We treated 376 embryos from 96patients with repeated IVF failures (two to four attempts) (groupA) and 397 embryos from 111 patients undergoing IVF for thefirst time (group B). Embryos were transferred immediately afterthe laser treatment. Both groups were compared to control groups(A' and B') whose embryos were transferred with intact zonapellucida (ZP). The resulting clinical pregnancies were 41 inA and 44 in B versus 24 hi A' and 23 in B' respectively. Thepregnancy rates per patient were 42.7 and 39.6% versus 23.1and 19% in the control groups (P < 0.05), while the implantationrates per embryo were 12.2% in A and 11.8% in B versus 13 and7.1%. These results show that laser zona thinning of human embryosat 48 h after egg retrieval significantly increases the implantationand pregnancy rate (P < 0.05).     

Pregnancies, growth and development of children conceived by subzonal injection of spermatozoa.

Subzonal injection of spermatozoa (SUZI) was one of the first micromanipulation techniques efficient in treating male factor infertility and unexplained in-vitro fertilization failures. The aim of this retrospective study was to evaluate the in-vitro development of embryos conceived by SUZI, the obstetric outcome, the rate of congenital malformations and subsequent follow-up in children. Fifty-five pregnancies were obtained between 1991 and 1994 (54 after fresh embryos were transferred and one after cryopreserved embryos were transferred). Among the 50 clinical pregnancies, there were seven miscarriages (14%) and two ectopic pregnancies (4%). Among the 41 resulting evolutive pregnancies, the discovery of one anencephaly led to a medical abortion. Forty deliveries including six twin pregnancies occurred, leading to the births of 45 live neonates and one stillbirth. The gender distribution of the offspring included 17 males and 29 females (ratio 0.59:1). Birth weight, length and head circumference were within the expected ranges. Two children presented a malformation: the first one had one thumb with congenital shelf and the second a polymalformative neurological syndrome. Growth curves were normal for all these children except one (weight above the 2 SD curve). Medical follow-up detected no pathological features in these children apart from a physical disability in one girl. In this small series a 4.2% rate of malformation was observed, particularly affecting the neural tube, in SUZI offspring. However, no firm conclusions can be drawn since the study was carried out on a small cohort. SUZI is no longer performed but these observations suggest that it is necessary to collect extensive data about children conceived by microfertilization.     

Comparison of SUZI and ICSI for severe male factor

We compare the results of subzonal insemination (SUZI) and intracytoplasmicsperm injection (ICSI) carried out between February 1993 andend of August 1994. A total of 232 couples underwent 302 cyclesof micro-assisted fertilization (79 patients had SUZI for atotal of 93 cycles, 153 patients ICSI for a total of 209 cycles).The indications for treatment were obstructive azoospermia in35 cycles, ejaculatory failure with severely low sperm countin 7 cycles, and failure of fertilization in a previous IVFcycle or less than 10% of oocytes fertilized in 87 cycles. In173 cycles the indication for treatment was a poor semen parameter.Patients undergoing ICSI had significantly higher fertilizationrates [43 (728/1692) versus 22.3% (151/676), ² = 86.308, P <0.0001], better chances of embryo transfer [95 (199/209) versus73% (68/93), ² = 30.671, P < 0.001], and greater numbersof embryos transferred (2.4 ± 0.9 versus 1.6 ±1.2 F = 42, P < 0.0001) than patients who had SUZI. Eighteenpatients became pregnant following the SUZI procedure, a pregnancyrate of 19% per egg collection, compared with 28% for thosewho underwent the ICSI procedure, where 58 out of 209 becamepregnant. The pregnancy rate was similar in those who underwentembryo transfer, whether they had ICSI or SUZI (29.2 and 28.6%respectively). Overall, the pregnancy rate doubled with eachnumber of embryos transferred, so it was 8.9% when one embryowas transferred, which increased to 18.3% when two embryos weretransferred, and this rose to 37.7% when three embryos weretransferred. There was no significant difference in the pregnancywastage rate between SUZI and ICSI. None of the offspring fromeither SUZI or ICSI showed any evidence of fetal abnormalities.Pregnancy rate was negatively correlated, with sperm progressionbeing 36% (36/100) if progression was <2 and 19.8% (40/202)if it was 2 (² = 8.99, P < 0.002). ICSI therefore providesa higher number of embryos available for transfer and shouldbe the primary treatment for severe male factor infertility.     

Ultrastructural observations in human oocytes and preimplantation embryos after zona opening using an erbium-yttrium-aluminium-garnet (Er:YAG) laser

For more than 3 years we have performed laser-assisted hatching prior to embryo transfer in patients with recurrent implantation failure using an erbium-yttrium-aluminium-garnet (Er:YAG) laser system that operates in the infrared region of the light spectrum. The laser beam is guided through a quartz fibre and is brought into direct contact with the zona pellucida. This study was undertaken to evaluate the ultrastructural effects of this laser on the zona pellucida and underlying cell membrane of unfertilized human oocytes and pathologically fertilized preimplantation embryos using light and scanning electron microscopy. The Er:YAG laser produces an almost circular zona opening in the shape of a truncated cone tapering off towards the inside, with a mean diameter of 18 mm. The exact diameter of the drilled site depends on the diameter of the fibre tip and the total number of pulses applied. After laser interaction, the zona matrix and the surface of the underlying ooplasm membrane showed no degenerative alterations. We conclude that the Er:YAG laser is an effective microsurgical tool for achieving reproducible, precise zona openings particularly suitable for purposes of assisted hatching because of their characteristic shape.      

Developmental competence of mouse embryos following zona drilling using a non-contact holmium: yttrium scandian gallium garnet (Ho: YSGG) laser system

The purpose of this study was to assess the efficacy of theholmium: yttrium scandian gallium garnet (Ho:YSGG) laser, operatingin a pipette-free, non-contact mode, to assist hatching andsustain normal embryonic development. Two-cell mouse embryoswere recovered and assigned to laser-assisted hatching (LAH)treatment or control human tubal fluid (HTF) culture with orwithout serum (HTF-s, HTF-o) or with late serum supplementation(HTF-o/s). The basic experimental apparatus for LAH consistedof a stationary 2.1 µm Ho: YSGG laser beam directed througha mechanical shutter into an input port of a Zeiss Axiomat invertedmicroscope. Fewer (P < 0.05) embryos developed to the blastocyststage in the HTF-s group (81%) than in the LAH (90%), HTF-o(94%) and HTF-o/s (92%) groups. The level of hatching was significantlyincreased (P < 0.01) after the LAH treatment (57%) comparedto HTF-o/s (32%), HTF-s (18%) or HTF-o (5%). Implantation rateswere not significantly impaired following the LAH treatment(21%). These data demonstrate that LAH using the Ho: YSGG laseris a simple, accurate and effective procedure for assisted hatching.     

A comparative analysis of embryos derived from routine in-vitro fertilization and subzonal microinsemination

Embryos obtained from patients undergoing routine in-vitro fertilization(IVF) and embryo transfer were compared with those undergoingsubzonal microinsemination (SUZI) for male factor infertility.Overall, the proportion of cleaved embryos was significantlyhigher in the IVF group in comparison with the SUZI group at48 h post-insemination [1533 out of 1609 (95.3%) versus 776out of 952 (81.5%)]. The mean ± SD grading score of theIVF-derived embryos of 3.61 ± 0.50 was significantlybetter than that for SUZI of 2.97 ± 0.86 (P < 0.0005)at the same time. The implantation rates following the replacementof IVF or SUZI embryos at 48 h were comparable: 14.3 and 10.0%respectively. However, the IVF embryo implantation rate of 15.1%at 72 h was significantly better than that following the replacementof SUZI embryos at either 48 (10.0%) or 72 h (8.0%). The replacementof SUZI-derived embryos at 48 h resulted in significantly higherpregnancy (25.0%) and implantation rates (10.0%) than at 72h, with rates of 10.8 and 8.0% respectively. Similarly, theoverall embryo quality deteriorated following in-vitro culturefor up to 72 h. The clinical pregnancy loss rate (33.0%) washighest following the replacement of SUZI embryos at 72 h, althoughthe data were limited. It is suggested that these data indicatethat a combination of in-vitro manipulation, the injection ofmultiple spermatozoa into the subzonal space and probably thegenomic capacity of spermatozoa derived from poor-quality semenmay contribute to the poorer outcome of embryo development followingSUZI. Prolonged in-vitro culture beyond 48 h appears to be deleteriousto the development of SUZI cleaved embryos and the subsequentoutcome of treatment, and hence should be avoided.     

Higher success rate by intracytoplasmic sperm injection than by subzonal insemination. Report of a second series of 300 consecutive treatment cycles

Subzonal insemination (SUZI) and intracytoplasmic sperm injection(ICSI) were carried out in 300 treatment cycles in couples unableto be helped by coventional in-vitro fertilization treatment.More oocytes were damaged by ICSI (13.5%) than by SUZI (7.1%).The normal fertilization rate was substantially higher afterICSI (51.0%) than after SUZI (14.3%) and was related to thesemen characteristics. The cleavage rate was similar for bothprocedures (77%). After 217 embryo transfers (72.3% of the treatmentcycles) 66 pregnancies were established, i.e. pregnancy ratesof 22.0% per started cycle and 30.4% per embryo transfer. Sofar, pregnancy loss has occurred in 27.3% of the pregnancies,nine healthy children have been born after eight deliveriesand 41 clinical pregnancies are progressing uneventfully. Chorionicvillus sampling or amniocentesis have been performed in 35 pregnanciesand 39 normal fetal karyotypes have been obtained after cytogeneticanalysis.     

The influence of subzonal microinsemination of oocytes failing to fertilize in scheduled routine in-vitro fertilization cycles

The subzonal microinsemination (SUZI) of oocytes failing tofertilize following routine in-vitro fertilization (IVF) inseminationwas studied in comparison to routine reinsemination. The datapresented indicate that fertilization rate was significantlybetter with SUZI (23.4%) than with reinsemination (8.3%). Thepercentage of cleaved replaceable embryos generated was alsosignificantly higher following SUZI than with reinsemination(96.6% versus 66.7% respectively). SUZI led to a significantlyhigher increase in the percentage of additional number of fertilizedoocytes (100%), fertilization cycles (185%), embryos replaced(108%) and embryo replacement cycle over that generated by initialinsemination. These were in comparison to 26, 14.3, 11.6 and15%, respectively, as a result of reinsemination. No pregnancyoccurred following replacement of embryos generated from reinsemination.Six pregnancies resulted from replacement of embryos followingSUZI. We suggest therefore that SUZI should be the preferredoption of practice when oocytes have failed to fertilize followinginitial insemination for routine IVF.     

Er：YAG激光治疗慢性牙周炎的临床疗效：随机对照试验的Meta分析

目的：比较并评价在慢性牙周炎治疗中,Er：YAG激光的疗效是否优于根面平整术（Scaling and Root Planing,SRP）。方法：检索外文数据库Springerlink、OVID、Embase、Pubmed和中文数据库万方、维普、中国知网、中国生物医学文献数据库,收集自建库到2013年l2月公开发表的关于Er：YAG治疗慢性牙周炎随机对照试验的文献,随访时间不得少于三个月。采用Jadad法对文章质量进行评价,并使用Stata12.0对治疗三个月、六个月及十二个月后两组牙周探诊深度和临床附着水平的改变值进行Meta分析。采用I2检验检测不同研究间的异质性。结果：共有8篇文献符合纳入和排除标准,Meta分析结果显示三个月、六个月及十二个月后,Er：YAG组与SPR组相比,牙周探诊深度差异无统计学意义,附着水平的差值也无统计学意义。结论：Er：YAG激光治疗牙周炎的短中期临床疗效好,可作为SPR的辅助疗法甚至替代疗法,但目前尚无足够的证据证明Er：YAG激光的临床疗效优于SPR。由于纳入研究的数量有限,且只有2篇文献为高质量研究,因此,上述结论仍需更多高质量的研究进一步证实。     

Endocrinology: Micromanipulation of mouse gametes with laser microbeam and optical tweezers

Micromanipulation of mouse gametes with a commercially availablecompact laser microbeam system was studied. Both the normalin-vitro fertilization (IVF) group and the laser zona dissection(LZD) group were tested under normal (2X10⁶ motile spermatozoa/ml)and low (500 000 motile spermatozoa/ml) insemination conditions.Subzonal insemination (SUZI) was also tried in a small groupof gametes and the results were compared with those of the lowinsemination groups. Fertilization rates and blastocyst formationrates for the IVF and the LZD-treated groups were respectively53 and 60% and 60 and 78%, which were not significantly different.However, under low insemination conditions, the results weresignificantly better in the LZD-treated group (58% fertilizationrate and 83% blastocyst formation rate) compared to the resultsof the IVF group (33 and 48%) (P < 0.05). The SUZI-treatedgroup showed the lowest fertilization rate (18%). No significantdifference between the LZD and the IVF group was observed withrespect to parthenogenetic activation. LZD has a beneficialeffect on fertilization rates in cases of reduced sperm qualit.     

Microsurgical fertilization and teratozoospermia

Semen parameters were correlated with the outcome of partial zona dissection (PZD) in 42 couples with male factor infertility. Although fertilization rates were reduced, 12% of the embryos implanted following replacement. Spermatozoa from teratozoospermic sperm populations were able to fuse with oocytes following zona penetration through the artificial gaps. PZD followed by insemination with less than 5% normal spermatozoa led to 20 embryos which, upon replacement, did not implant. Motility and sperm count were not clearly correlated with the outcome of PZD and are therefore less useful indicators for patient selection. Teratozoospermic patients who previously failed to fertilize were compared to a group of similar patients who had not attempted IVF before. Although fertilization was significantly improved in first-time patients, 41% of the patients whose spermatozoa were initially unable to fertilize had at least one embryo when PZD was performed. Several pregnancies were established in this group. Subzonal sperm insertion (SZI) and PZD were compared in 19 patients using sibling oocytes. A significant fraction of spermatozoa from infertile men were able to fuse with the oolemma when directly inserted into the perivitelline area. Using a sucrose solution to shrink the ooplasm, only 1% of the oocytes were damaged during SZI. Monospermic fertilization rates following PZD and SZI were 15 and 16%, respectively. Both micromanipulation methods were successful in most patients. However, in two small groups of patients, only one technique resulted in fertilization.     

Laser-assisted zona pellucida thinning prior to routine ICSI

BACKGROUND: In MII oocytes showing difficult oolemma breakage, ICSI can cause an increase in the degeneration rate. This may be overcome by laser-assisted ICSI using a 5-10 micro m opening in the zona pellucida for injection. However, such a small opening might impair the hatching process, especially if assisted hatching is applied in addition. In order to prevent this, the present study used routine injection through an area of zona pellucida in which laser zona thinning had been applied, providing for both a reduced mechanical stress to the oocyte and assisted hatching. METHODS: This prospective study involved 100 cycles with 1016 MII oocytes. Conventional ICSI (control group) was compared with a modified laser-assisted ICSI (study group) in sibling oocytes. In the latter group oocytes were injected through an extended area of zona thinning. RESULTS: Degeneration rate was significantly lower in the study group (P < 0.004). There were no differences in fertilization, or formation and quality of blastocysts. In the study group embryo quality on day 2 was significantly better (P = 0.004) and herniation of day 5 blastocysts was increased (P = 0.005). Rates of implantation and pregnancy were not affected. However, on day 3 laser-assisted ICSI proved beneficial (P = 0.038) in terms of clinical pregnancy rate. CONCLUSIONS: The new method combines a less invasive ICSI technique with assisted hatching. Our preliminary data indicate that in addition to an improved oocyte survival, this new approach increases the hatching rate in vitro, which may explain the increase in pregnancy rate, at least in day 3 transfers.     

Routine application of partial zona dissection for male factor infertility

Partial zona dissection (PZD) increases the chances of fertilization by improving the access of spermatozoa to the perivitelline space (PVS) helping those spermatozoa unable to penetrate the zona pellucida (ZP) and possibly those poorly able to penetrate the oolemma. Problems arise in assessing semen to decide which parameters might indicate defects of this nature. PZD, by circumventing the ZP, may also increase the rate of polyspermy, especially in infertility where ZP and oolemmal penetration are not defective. Given these drawbacks, we performed PZD as routine treatment for male infertility in 70 in-vitro fertilization cycles. In three different groups, PZD proved to be either effective, ineffective or unnecessary. In the first group of 35 cycles, fertilization was 23% with initial PZD and 33% with PZD reinsemination (36% and 41% polyspermy respectively). No fertilization occurred following conventional insemination (CONV). Four pregnancies occurred in this group. In a second group of 19 cycles, fertilization did not occur with either PZD or CONV. In the final group of 16 cycles, fertilization was similar following both PZD and CONV, but polyspermy was 48% in the PZD category. Transfer of mixed PZD and CONV embryos in this group yielded 10 pregnancies. Assessment of all patient and seminal profiles, and those in an oligozoospermic subcategory, revealed no parameters of relevance to success or failure with PZD. However, one subgroup in the group of total failure to fertilize did have a significantly lower percentage of normal morphology (P less than 0.005), suggesting that degree of teratozoospermia may be a prognosticator of success using PZD.     

Comparison of the results of human embryo biopsy and outcome of PGD after zona drilling using acid Tyrode medium or a laser

BACKGROUND: Zona pellucida opening for blastomere removal can be done by mechanical or chemical means, or by laser. So far, only limited data on the use of laser systems for zona drilling in cases of PGD are available. METHODS: Results of embryo biopsy and outcome of PGD in two periods were compared. In the first period, acid Tyrode medium was used for zona drilling. In the second period, zona drilling was performed by a 1.48 micro m infrared laser. RESULTS: In the first period, 59 cycles resulted in 53 biopsy procedures with 356 biopsied embryos. In the second period, these numbers were 69 cycles, 69 biopsy procedures and 402 biopsied embryos. Fewer blastomeres were intact (95.2%) after zona drilling with acid Tyrode than after laser zona drilling (98.3%, P = 0.02). Rates of positive HCG (37.5% versus 35.5%), ongoing pregnancy rates (31.3% versus 25.0%) and ongoing implantation rates (18.9% versus 14.9%) did not differ. CONCLUSIONS: The use of a laser for zona drilling in cases of PGD is an easier procedure and results in more intact blastomeres. Since similar pregnancy rates are obtained, it is advantageous to use a laser for zona drilling. Further follow-up is necessary to prove the safety of this procedure.