Advanced scheduling for zygote intrafallopian transfer is possible via the use of a hormone replacement cycle for patients who have experienced repeated implantation failures.

PURPOSE: Zygote intrafallopian transfer (ZIFT) is an effective option for patients who have experienced repeated implantation failures (RIF) in assisted reproductive technology (ART) treatment. However, advance planning for the day of the operation can be problematic. Using a hormone replacement cycle (HRC) makes it possible to plan for the day of ZIFT. In the present study, we evaluated whether HRC-ZIFT is useful for RIF patients who have experienced difficulties obtaining morphologically good embryos in vitro. METHODS: A total of 55 patients with a history of five or more unsuccessful transfers received HRC-ZIFT between June 2008 and June 2013. The oocyte pick-ups were performed and the oocytes showing two pronuclei (2PN) were cryopreserved. After receiving more than five 2PN oocytes, the operation day was scheduled in advance, and as a consequence, a HRC was started and ZIFT was performed. The clinical outcomes were evaluated. RESULTS: The average age of the patients was 39.3 years, and the previous OPU and ET attempts numbered 7.5 and 6.9, respectively. The number of previously transferred embryos was 11.8, and the number of morphologically good embryos (MGEs) was only 1.2. The number of transferred 2PN oocytes was 6.7, and the subsequent pregnancy rate was 23.6 %. No ectopic or multiple pregnancies were observed, but there were 6 cases of miscarriage. CONCLUSION: Among RIF patients, in particular those who have difficulty obtaining MGEs in vitro, ZIFT might be a useful option. The HRC allows patients and medical staff to plan for the operation day in advance.

Efficient reproduction of cynomolgus monkey using pronuclear embryo transfer technique.

One of the technical bottlenecks in producing nonhuman primate models is that current assisted reproductive techniques, such as in vitro culture and frozen conservation of multicell-stage embryos, often result in poor embryo quality and subsequently lead to low birth rates. We investigated whether pronuclear embryo transfer can be used as an effective means for improving pregnancy and live birth rates of nonhuman primates. We collected 174 metaphase II oocytes by laparoscopy from 22 superovulated mature females and then fertilized these eggs using either in vitro fertilization or intracytoplasmic sperm injection, resulting in a 33.3% and a 50% fertilization rate, respectively. These 66 fertilized pronuclear-stage embryos were then tubally transferred to 30 recipients and led to 7 births and 1 abortion. Importantly, we observed that the highest live birth rate of approximately 64% was obtained when the transfer of pronuclear embryos was performed in the presence of new corpus luteum in the ovary of recipients between 24 h and 36 h after estradiol peak. Therefore, our experiments demonstrate that by matching the critical time window in the recipient's reproductive cycle for achieving optimal embryo-uterine synchrony, pronuclear embryo transfer technology can significantly improve the pregnancy rate and live birth of healthy baby monkeys. This efficient method should be valuable to the systematic efforts in construction of various transgenic primate disease models.

Office microlaparoscopic intrafallopian transfer of day one zygote versus day three embryo transfer after previous failed ICSI trials.

The objective of the study was to investigate whether transferring zygotes on day 1 would result in similar pregnancy rates compared to transferring cleavage stage embryos on day 3 in a prospective randomized trial, using the office microlaparoscopic procedure. Patients undergoing IVF/ICSI treatments were randomized to either day 1 or day 3 transfers after previous failed ICSI trials due to failed implantation. The primary outcome measure was pregnancy rate. Pregnancy rates were higher in day 3 group (55/131, 42%) when compared to day 1 (34/123, 28%, P = 0.024). Similarly, implantation rates were higher in day 3 group (P = 0.03). There were more cycles with cryopreservation in the day 1 group (P < 0.001). Embryo quality on day 3 was similar between pattern 0 and non-pattern 0 zygotes. Day 3 embryo transfers result in better pregnancy and implantation rates compared to day 1 zygote transfers.

Obstetric and neonatal outcomes after the transfer of vitrified-warmed blastocysts developing from nonpronuclear and monopronuclear zygotes: a retrospective cohort study.

OBJECTIVE: To evaluate the obstetric and neonatal outcomes after the transfer of vitrified-warmed single blastocysts developing from nonpronuclear (0PN) and monopronuclear (1PN) zygotes. DESIGN: Cohort study. SETTING: Affiliated hospital. PATIENT(S): This study was a retrospective analysis of 435 0PN and 281 1PN vitrified-warmed single blastocyst transfers, and 151 0PN and 75 1PN singletons, compared with 13,167 two-pronuclear (2PN) vitrified-warmed single blastocyst transfers and 4,559 2PN singletons, respectively. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Pregnancy rate (PR), abortion rate (AR), live birth rate (LBR), and singleton birthweight were the primary outcome measures. RESULT(S): PR, AR, and LBR were similar when compared between the 0PN and 2PN groups after vitrified-warmed blastocyst transfer. However, the 0PN group had a higher birthweights, higher z scores, and a greater proportion of very large for gestational age newborns. When comparing the 1PN and 2PN groups, we found that the PR was similar whereas the AR was higher and the LBR was lower. No differences were detected in the other neonatal outcomes. CONCLUSION(S): The results of the present study show that the transfer of 2PN blastocysts should be prioritized because of a higher AR and a lower LBR after 1PN blastocyst transfers and a higher birthweight after 0PN blastocyst transfers when compared with 2PN blastocyst transfers. Our data indicate the need for concern about the safety of 1PN and 0PN embryo transfers.

Analysis of pronuclear zygote configurations in 459 clinical pregnancies obtained with assisted reproductive technique procedures.

BACKGROUND: Embryos selection is crucial to maintain high performance in terms of pregnancy rate, reducing the risk of multiple pregnancy during IVF. Pronuclear and nucleolar characteristics have been proposed as an indicator of embryo development and chromosomal complement in humans, providing information about embryo viability. METHODS: To correlate the zygote-score with the maternal age and the outcome of pregnancy, we analyzed the pronuclear and nucleolar morphology, the polar body alignment and the zygote configuration in 459 clinical pregnancies obtained by IVF and ICSI in our public clinic in Reggio Emilia, Italy. We derived odds ratios (OR) and Corenfield's 95% confidence intervals (CI). Continuous variables were compared with Student's t-test; P lower than .05 was considered statistically significant. RESULTS: We observed a significant increase of "A" pronuclear morphology configuration in 38-41 years old patients in comparison to that lower than or equal to 32 years old and a significant decrease of "B" configuration in 38-41 years old patients in comparison to that lower than or equal to 32 and in comparison to that of 33-37 years old. Related to maternal age we found no significant differences in P1 and in P2 configuration. We found no correlation between zygote-score, embryo cleavage and embryo quality. CONCLUSIONS: Our results confirm the limited clinical significance of zygote-score suggesting that it can not be associated with maternal age, embryo cleavage and embryo quality. The evaluation of embryo quality based on morphological parameters is probably more predictive than zygote-score.

Comparison of different cryopreservation techniques: higher survival and implantation rate of frozen-thawed mouse pronuclear embryos in the presence of beta-mercaptoethanol in post-thaw culture.

The objective of this study was to investigate the effects of beta-mercaptoethanol (ß-ME) on post-thaw embryo developmental competence and implantation rate of mouse pronuclear (PN) embryos that were cryopreserved after slow freezing, solid surface vitrification (SSV) or open-pulled straw (OPS) vitrification methods. Mouse PN embryos were cryopreserved by using slow freezing, SSV and OPS methods. After cryopreservation, freeze-thawed PN embryos were cultured up to blastocyst stage in a defined medium supplemented without or with 50 µM ß-ME. The blastocyst formation rate of embryos that were cryopreserved by slow freezing method (40.0%) or vitrified by OPS method (18.3%) were lower than those vitrified by SSV method (55.6%) and fresh embryos (61.9%) in the absence of 50 ß-ME in the culture media (p < 0.05). The blastocyst formation rate of embryos that were cryopreserved by slow freezing method (53.1%) or by OPS method (41.9%) were lower than those vitrified by SSV method (79.5%) and that of fresh (85.7%) in the presence of ß-ME in the culture media (p < 0.05). The embryos transfer results revealed that the implantation rate of blastocyst derived from mouse PN embryos vitrified by SSV method (31.9% vs 51.2%) was similar to that of the control (39.0% vs 52.5%), but higher than those cryopreserved by slow freezing (28.2% vs 52.0%) and by OPS method (0.0% vs 51.2%) (p < 0.05). In conclusion, supplementation of ß-ME in an in vitro culture medium was shown to increase survival of embryo development and implantation rate of frozen-thawed mouse PN embryos after different cryopreservation protocols.

Comparison of pregnancy and implantation rates in zygote intrafallopian transfer and uterine embryo transfer for nontubal infertility.

We carried out a prospective randomized trial on 220 couples with nontubal factor infertility to compare pregnancy rates and implantation rates after zygote intrafallopian transfer (ZIFT) and uterine embryo transfer (UET). The zygote was transferred by laparoscopy into the fallopian tube 24 hours after oocyst retrieval. UET was performed 72 hours after retrieval with abdominal sonography guide. Transfer was performed in 102 cycles in the ZIFT and 100 cycles in the U ET group. The pregnancy and implantation rates were significantly higher in the ZIFT group (42.1% and 11.7%) than in the UET group (21.0% and 7.8%) (P < 0.05). ZiFT could be considered for couples who have limited time and adequate financial support.

Noninvasive embryo selection: kinetic analysis of female and male pronuclear development to predict embryo quality and potential to produce live birth.

OBJECTIVE: To evaluate a noninvasive method of examining euploid embryos, focusing on kinetic analyses, from second polar body extrusion to pronuclear membrane breakdown (PNMBD). DESIGN: Retrospective embryo cohort study. SETTING: Private IVF clinic. PATIENT(S): 213 frozen-thawed single blastocyst transfers. INTERVENTION(S): Fertilized oocytes were recorded by means of time-lapse photography, followed by kinetic analysis of female and male pronuclei (PNs). MAIN OUTCOME MEASURE(S): The differences in size between the 2PNs in embryos resulting in live births compared with those of embryos from failed pregnancies were analyzed according to sequential size from early PN stages to PNMBD. RESULT(S): It was found that the difference in areas between male and female PNs immediately before PNMBD is a better predictor of embryo quality if this difference is below a known cutoff value. The size of male PNs 8 hours before the onset of PNMBD should be larger than female PNs (B). The difference in size between male and female PNs 8 hours before PNMBD should be larger than the difference in their size immediately before PNMBD. When normal embryos were defined using the equation (A∪C)∩B, the birth rates for in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) were 68.1% and 50.0%, respectively. For the remaining embryos, defined as abnormal according to the above criteria, birth rates were 9.4% for IVF and 4.2% for ICSI. CONCLUSION(S): We have developed a method for noninvasive embryo evaluation by means of the kinetic analysis of female and male PN growths. This method should enable us to select embryos that have a higher potential for healthy births.

Identification of biparental and diploid blastocysts from monopronuclear zygotes with the use of a single-nucleotide polymorphism array.

OBJECTIVE: To select normal fertilized diploid blastocysts in patients who had only monopronucleated (1PN) embryos for transfer. DESIGN: Experimental study. SETTING: University-affiliated center. PATIENT(S): Couples who were undergoing intracytoplasmic sperm injection treatment and had 1PN blastocysts. INTERVENTION(S): In a preliminary test, limited cells of parthenogenetic human embryonic stem cells (phESCs) and normal fertilized blastocysts were analyzed with the use of a low-density single-nucleotide polymorphism (SNP) array to identify the distribution pattern and rate of heterozygosity. In the clinical application, 1PN blastocysts were analyzed with the use of the SNP array. Only diagnosed normal blastocysts were transferred. The diagnosed uniparental blastocysts were validated by imprinted gene expression. MAIN OUTCOME MEASURE(S): Distribution pattern and rate of heterozygosity between parthenogenesis and normal fertilization. RESULT(S): In the pretest, phESCs exhibited distinct distribution pattern and lower rate of heterozygosity, compared with normal fertilized blastocysts after SNP analysis. In particular, homozygous hESCs showed a panhomozygosity distribution pattern, hybrid phESCs showed a partial homozygosity distribution pattern, and normal fertilized blastocysts exhibited a panheterozygosity distribution pattern with an average of 20.21% heterozygosity rate; 13.6% was found to be the minimum cutoff to predict normal fertilized samples. In the clinical application, 24 1PN blastocysts were analyzed; 10/24 showed chromosomal abnormalities, 3/24 showed panhomozygosity with 0.45%-0.8% heterozygosity, and 1/24 showed partial homozygosity with 6.54% heterozygosity. The remaining 10 blastocysts, with a panheterozygosity distribution pattern and higher genomic heterozygosity rate, were diagnosed as normal-fertilization diploid embryos; three were transferred and resulted in two healthy newborns. CONCLUSION(S): The low-density SNP array might serve as a cost-effective method to identify biparental origin and diploid 1PN blastocysts for transfer.

Strain-dependent high-level expression of a transgene for manganese superoxide dismutase is associated with growth retardation and decreased fertility.

Manganese superoxide dismutase (MnSOD) is essential in protecting mitochondria against the damaging effects of superoxide radicals (O(2)(*-)), and increased expression of MnSOD protects cells and transgenic animals from various forms of oxidative stress. In addition, increased levels of MnSOD have been shown to slow down cell growth and induce differentiation. To study the effects of high MnSOD levels in vivo, we generated a series of transgenic mice using a mouse genomic sequence under control of the endogenous promoter. Four transgenic lines produced by pronuclear DNA injection exhibited up to 2-fold elevated MnSOD levels in brain and heart. However, using an embryonic stem cell approach, a line having 10-fold elevated MnSOD levels in the brain and 6- to 7-fold elevated levels in the heart and kidney was generated. Surprisingly, the genetic background of this transgenic line influenced the expression level of the transgene, with DBA/2 (D2) and C57BL/6 (B6) mice exhibiting low- and high-level transgene expression, respectively. This difference was the result of an increased transcription rate of the transgene. High-level MnSOD expression in B6 animals was associated with small size, male infertility, and decreased female fertility. These features are absent on the D2 background and indicate that high levels of MnSOD activity may interfere with normal growth and fertility.

Number of transferred embryos: how to reduce multiple pregnancies.

Because the diagnostic tools for predicting whether an early cleavage stage embryo can lead to a viable pregnancy are still elusive, transfer of more than one embryo remains quite common. However, the only way to reduce multiple pregnancies, considered as the main adverse effect of assisted reproductive technology, is to transfer a single embryo. In countries such as Switzerland and Germany, the law allows cryopreservation only at the 2-pronuclear stage. This restricts considerably the possibility of selecting the embryos to be transferred. Therefore, a good cryopreservation program at the 2-pronuclear stage is an essential tool to optimize the efficiency of in vitro fertilization (IVF). We therefore recommend the Cumulated Singleton Delivery Rate (CUSIDERA) as a measure of standard IVF efficiency. This rate averages approximately 23.5% when calculated over the last 10 years in our unit and reaches a value above 35% for patients with more than 10 zygotes. Elective single-embryo transfers and the decrease of iatrogenic multiple pregnancies in IVF remain dependent on better prognostic tools for the appropriate selection of patients, gametes, and zygotes.

In vitro development and implantation rates of fresh and cryopreserved sibling zygotes.

OBJECTIVE: To compare the developmental potential of cryopreserved human zygotes after thawing to sibling zygotes that were transferred without cryopreservation. METHODS: Retrospective analysis of embryo data and pregnancy outcome for all in vitro fertilization (IVF) patients who had sufficient zygotes to allow fresh embryo transfer and cryopreservation of additional sibling zygotes for later use. RESULTS: Zygotes survived cryopreservation at a high rate (87%). After thawing, cryopreserved zygotes developed at rates similar to those of fresh zygotes. Pregnancy occurred at similar rates after replacement of fresh embryos (27.9%) or replacement of cryopreserved-thawed zygote-derived embryos (24.3%). CONCLUSIONS: Human embryos can be cryopreserved at the pronuclear zygote stage with little loss of developmental potential. Cryopreservation allowed a reduction in the number of embryos transferred during an IVF retrieval cycle, thereby reducing the occurrence of multiple pregnancy. The total cumulative pregnancy rate per retrieval cycle doubled when pregnancies from cryopreserved-thawed zygotes were added to those originating from fresh zygotes.

Zygote intrafallopian transfer in patients with tubal factor infertility after repeated failure of implantation with in vitro fertilization-embryo transfer.

OBJECTIVE: To evaluate the efficacy of zygote intrafallopian transfer (ZIFT) in terms of implantation and pregnancy rates in patients with tubal factor infertility and repeated implantation failure in IVF-ET cycles. DESIGN: Retrospective analysis of ZIFT cycles. SETTING: An IVF unit in a university hospital. PATIENT(S): Criteria for patient selection for ZIFT included at least four failures of implantation in IVF-ET cycles in which at least 3 embryos were replaced per transfer and a cause of infertility diagnosed as male, unexplained, or tubal factor with proof of one patient tube. INTERVENTION(S): Four to six zygotes were transferred by laparoscopy into the fallopian tube 24-26 hours after oocyte retrieval. MAIN OUTCOME MEASURE(S): Implantation and pregnancy rates were determined in 112 ZIFT cycles performed in 81 patients with repeated failure of implantation. Results were further stratified for patients with tubal factor (n = 15) and patients without tubal factor (n = 66). RESULT(S): The pregnancy and implantation rates for all ZIFT cycles were 35.1% and 11.1%, respectively. Pregnancy and implantation rates per cycle in patients with tubal factor versus patients without tubal factor were 26.6% versus 37.1% and 9.4% versus 11.4%, respectively. CONCLUSION(S): ZIFT can be considered as a mode of treatment for patients with repeated failure of implantation in IVF-ET and with tubal factor with proved patency of one tube.

Frozen zygote intrafallopian transfer: a successful approach for transfer of cryopreserved embryos.

OBJECTIVE: To assess whether frozen ET to the fallopian tube is a possible alternative for cryopreserved embryos. DESIGN: Fifty-four patients (mean age 35 years) participated, in which their embryos were cryopreserved in 1.5 M propanediol at the pronuclear or two-cell stage. Each patient then underwent a steroid replacement cycle consisting of oral micronized 17 beta-E2 2 mg on days 2 to 4, 4 mg on days 5 to 7, 6 mg on days 8 to 10, and 8 mg from day 11 on. Serial ultrasounds were performed to evaluate the endometrium until an optimal thickness of > or = 10 mm triple layer was achieved. At this time, 100 mg IM progesterone was initiated and the zygote intrafallopian transfer (ZIFT) procedure was performed on the third day of P administration. The average number of embryos transferred was 4.4. RESULTS: Twenty-two clinical pregnancies resulted, giving a pregnancy rate of 41%. Eight miscarriages occurred and one ectopic pregnancy resulted, giving a live birth rate of 24%. Implantation rate was 10.8%. The highest chance of pregnancy was seen in patients who never had a previous IVF, GIFT, or ZIFT (61%). CONCLUSION: This is the first report of a series of frozen ETs to the fallopian tubes. These results indicate that tubal transfer may offer a protective benefit of the tubal environment and avoidance of endometrial trauma, and should be added to our armamentarium of replacing cryopreserved embryos.

A randomized study of transcervical intrafallopian transfer of pronucleate embryos controlled by ultrasound versus intrauterine transfer of four- to eight-cell embryos.

OBJECTIVE: To establish the value of transcervical intrafallopian transfer of zygotes and the accuracy of fallopian cannulation. DESIGN: A prospective randomized study, comparing ultrasonically controlled transcervical intrafallopian transfer of zygotes with intrauterine transfer of cleaved embryos. SETTING: Department of IVF of the Rotterdam Academic Hospital. PATIENTS: One hundred forty-five patients with patent tubes entered the IVF program. MAIN OUTCOME MEASURE: Pregnancy rates in both groups and ultrasound (US) assessment during fallopian cannulation and ET. RESULTS: Transvaginal cannulation of the tube appears not to be sufficiently accurate when performed without US guidance. Catheter damage occurred in many cases. The previously reported superior implantation rate after intrafallopian transfer in comparison with intrauterine transfer could not be confirmed. CONCLUSIONS: Intrauterine transfer of cleaved embryos remains the method of choice in IVF.

Effect of encapsulation on development of mouse pronuclear stage embryos in vitro.

Pronuclear stage embryos with intact (ZI), slit (ZS) or completely removed (ZF) zona pellucida were encapsulated with an artificial zona pellucida (AZP) made of 1.5% sodium alginate. Embryos were cultured in KSOM medium with or without protein and their development in vitro to the blastocyst stage was recorded. AZP significantly (P < 0.05) improved the development of embryos to the blastocyst stage regardless of the presence of the natural zona pellucida. The encapsulated embryos developed at a higher rate (P < 0.05) in the absence of protein as compared with non-encapsulated embryos. Furthermore, the cell contacts at the 4-cell stage were significantly improved (P < 0.05) with encapsulation. AZP improved (P < 0.05) the development of pronuclear stage embryos with a slit zona pellucida to morula and blastocyst stages as compared with ZS embryos. It is concluded that AZP improves the in vitro development of pronuclear stage embryos with intact or completely removed zona pellucida as well as micromanipulated embryos to the blastocyst stage.

Transcervical gamete and zygote intrafallopian transfer. Does it enhance pregnancy rates in an assisted reproduction program?

OBJECTIVE: To evaluate the role of early tubal transfer procedures, we compared outcomes of transcervical gamete intrafallopian transfer (TC-GIFT) and transcervical zygote intrafallopian transfer (TC-ZIFT) versus in vitro fertilization/embryo transfer during the first two years of our assisted reproduction (AR) program. STUDY DESIGN: Prospective, nonrandomized, concurrent, controlled comparison of TC-GIFT and TC-ZIFT pregnancy outcomes versus those after IVF-ET. All cycles for patients less than age 39 undergoing transfer of at least three viable oocytes, zygotes or embryos in the first two years of our program were included. Patients with normal fallopian tubes underwent TC-GIFT (n = 9) or TC-ZIFT (n = 12), whereas those with tubal compromise underwent IVF-ET (n = 28). RESULTS: Implantation rates were 4.2% for TC-ZIFT, 2.8% for TC-GIFT and 3.7% for combined TC procedures as compared to 7.4% for IVF-ET. Delivery rates were no different for the TC procedures than the IVF-ET procedures (14%). Patients ages, number of oocytes retrieved and number transferred were comparable between the TC and IVF-ET groups. CONCLUSION: TC-GIFT and TC-ZIFT did not enhance the pregnancy outcome as compared to IVF-ET in the first two years of our AR program. Ultrasound-directed tubal catheterization is harder to learn and more difficult and expensive to perform than simple uterine embryo transfer. Since we could not demonstrate an improved outcome for TC transfers even in a new AR program, IVF-ET and laparoscopic GIFT are now our procedures of choice.

Gamete intrafallopian transfer. An overview.

Gamete intrafallopian transfer involves a direct transfer of both human gametes, sperm and oocytes, into the fallopian tube. Since the first report of a successful pregnancy following the use of this technique by Asch et al in 1984, its role in the treatment of infertile women with patent tubes has been established. Recent data demonstrate a 34.4% clinical pregnancy rate, with the highest pregnancy rate achieved in infertile women due to endometriosis or unexplained infertility.

Laparoscopic recovery of pronuclear-stage goat embryos.

The oviducts of 16 Saanen does, superovulated with follicle-stimulating hormone (FSH) and synchronised with prostaglandin F2 alpha were flushed 75 to 86 hours after the injection of prostaglandin. The mean (sd) ovulation rate was 13.7 (3.9). The flushings were directed orthograde through a flexible intravenous catheter, which was introduced into the oviduct via the infundibulum. The flushing medium was recovered by a balloon-catheter, which was placed in the uterine lumen near the uterotubal junction. Five does were flushed unilaterally either because they had one blocked oviduct or because they had ovulated on only one ovary. The overall embryo recovery rate was 72 per cent. Nine weeks later 11 of the donor ewes were examined laparoscopically and no adhesions of the reproductive organs were observed. Eight of these does were synchronised with progestagen-vaginal sponges, superovulated with FSH and their oviducts were flushed again. Their mean ovulation rate was 16.0 (4.3) and 86 per cent of the embryos were recovered. The optimal time to obtain pronuclear stage embryos was 75 to 78 hours after the injection of prostaglandin. All the embryos recovered within this period were at the pronuclear stage whereas 28 per cent of those recovered one to six hours later were at the two- or four-cell stage.

[Prognostic value of the pronuclear morphology pattern of zygotes for implantation rate]. / Wartosc prognostyczna oceny morfologicznej przedjadrzy zaplodnionych komorek jajowych na odsetek implantacji ludzkich zarodków.

INTRODUCTION: In ICSI and conventional IVF cycles, the embryos are usually selected for transfer based on evaluation of the cleavage speed and the extent of blastomere fragmentation. Pronuclear stage scoring system has been used in IVF recently as an additional parameter. OBJECTIVES: The aim of this study was to classify embryos from ICSI cycles according to the pronuclear scoring system and its influence on implantation rate. MATERIAL AND METHODS: 62 couples suffering from different types of infertility and treated by ICSI were included in our study. For each embryo, the following data were analyzed: pronuclei (PN) morphology, 16-20 hours after ICSI, and embryo morphology, about 40-42 (day 2) and 65-68 (day 3) hours after ICSI. The embryo transfer was performed on the third day after pick-up. RESULTS: In 55 (88.7%) cases we transferred at least one embryo from the zygotes of 0 or 1 or 2 pattern. The implantation rate was 30.6% (n = 19). In all of these cases the embryos have been derived from zygotes from pattern 0, 1 or 2. CONCLUSIONS: Pronuclear scoring system of zygotes appears to be a predictor of the implantation potential. Embryos derived from pattern 0, 1 and 2 of zygotes implant at a higher rate (p = 0.05).