Does assisted hatching pose a risk for monozygotic twinning in pregnancies conceived through in vitro fertilization?

Improved implantation rate after chemical removal of the zona pellucida

OBJECTIVE

To evaluate the implantation rate achieved after chemical removal of the zona pellucida from day 5 human in vitro-derived embryos.

DESIGN

Prospective, randomized, controlled study.

SETTING

A tertiary care infertility clinic.

PATIENT(S)

Two hundred fifty-seven patients undergoing IVF with transfer of morulas or blastocysts on day 5 after oocyte retrieval. All patients had had at least two previous implantation failures.

INTERVENTION(S)

Chemical removal of zona pellucida by using acidic Tyrode's solution vs. no removal (controls).

MAIN OUTCOME MEASURES

Clinical pregnancy rate and implantation rate per transfer.

RESULT(S)

Embryos without zona pellucida implanted at nearly twice the rate of control embryos (15.7% vs. 27.5%). The pregnancy rate was also significantly higher in the zona pellucida-free group than the control group (31.0% vs. 46.1%). Removal of zona pellucida was most effective in embryos with delayed development, which reached the morula or early cavitating stage on day 5 of in vitro culture (implantation rate, 12.1% vs. 25.7%).

CONCLUSION(S)

Chemical removal of zona pellucida from day 5 in vitro cultured human embryos is an effective and safe method of significantly improving the implantation rate, especially of embryos with delayed development.

Incidence of monozygotic twinning with blastocyst transfer compared to cleavage-stage transfer

OBJECTIVE

To evaluate the incidence of monozygotic twinning (MZT) in pregnancies conceived after blastocyst transfer compared to cleavage-stage transfer.

DESIGN

Retrospective study.

SETTING

University IVF program.

PATIENT(S)

All IVF patients with viable pregnancies conceived during a 4-year period.

INTERVENTION(S)

Blastocyst transfer or day 3 ET.

MAIN OUTCOME MEASURE(S)

Incidence of MZT assessed by transvaginal ultrasound.

RESULT(S)

There were 11 incidences of MZT in 197 viable pregnancies (5.6%) with blastocyst transfer compared to 7 of 357 viable pregnancies (2%) with day 3 ET. In 10 of 18 pregnancies, MZT was observed in the setting of a higher order multiple gestation (6 of 11 for blastocyst transfer and 4 of 7 for day 3 ET). In the day 3 ET group, assisted hatching or intracytoplasmic sperm injection (ICSI) did not increase MZT (4 of 213, 1.9%) compared to cycles without zona breaching (3 of 144, 2.1%). Similarly, in the blastocyst-transfer group, ICSI did not increase the incidence of MZT (4 of 74, 5.5% for ICSI and 7 of 123, 5.7% for non-ICSI IVF).

CONCLUSION(S)

Compared to day 3 ET, blastocyst transfer appears to significantly increase the incidence of gestations with MZT. This information should be taken into account when counseling patients about the pros and cons of extended culture.

Fertilization rate and preimplantation development after intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) is the treatment of choice in cases of male factor infertility. In the present review, all data from the literature regarding early fertlilization and preimplantation embryo development are analysed. ICSI seems to offer better fertilization rates than conventional IVF, even in the absence of a male factor and in prospective, randomized studies on sibling oocytes. Blastocyst formation is lower in ICSI than in IVF. This may be due to sublethal disturbances in oocyte architecture and function. Implantation and pregnancy rates, however, are similiar in ICSI and conventional IVF. Therefore, it can be concluded that ICSI offers a safe approach, as far as is known to date, for the treatment of male factor infertility. Embryo selection in cases of sublethal damage to oocytes seems to take place in the early preimplantation stages. Nor does the risk of monozygotic twinning, which was also proposed to be higher in ICSI compared with conventional IVF, seem to increase with this procedure.

Assisted reproductive technologies: toward improving implantation rates and reducing high-order multiple gestations

Despite striking progress in reproductive medicine over the past quarter century, the number of high-order multiple gestations are unacceptably high, largely as a result of the drive to maintain pregnancy rates in a competitive range. Morphologic criteria are currently used to define the reproductive competence of individual embryos but are imperfect predictors of implantation potential. Current and potential strategies to improve the selection of embryos are described. By the use of several of these approaches, it is hoped that the overall number of embryos that are transferred will be reduced, thereby also reducing the multiple gestation rate.

The role of expression of extracellular matrix proteins and epidermal growth factor receptor activity on fertilization capacity of testicular harvested spermatozoa

It has been suggested that multiple growth factors are crucial for spermatogenesis. We analyzed whether alterations on epidermal growth factor receptor activity and different expression pattern of extracellular matrix proteins had an impact on the fertilization capacity of spermatozoa and pregnancy rate after testicular sperm extraction and intracytoplasmic injection. Extracellular matrix proteins and epidermal growth factor receptor were immunohistochemically evaluated in testis of 88 patients with nonobstructive azoospermia. Testicular sperm extraction and intracytoplasmic injection procedure was also performed in 32 of the patients for whom mature sperm could be harvested from the testicular tissue. While collagen Type-IV and laminin activity percentages were 33.1% and 86.4% in motile sperm harvested testicular tissue, these activities were 23.3% and 89.3% in immotile sperm harvested testicular tissue, respectively. In addition, the mean epidermal growth factor receptor expression was higher in immotile than motile sperm obtained tissue (56.4% vs. 51.1%, P=0.4928). There was no statistically significant relationship between the extracellular matrix protein and epidermal growth factor receptor expression patterns and sperm motility, fertilization and pregnancy rates in testicular sperm extraction and intracytoplasmic injection. However, further studies are required to investigate the relationship between other growth factors and sperm fertilization capacity.

A novel approach for patients at risk for ovarian hyperstimulation syndrome: elective transfer of a single zona-free blastocyst on day 5

In this preliminary prospective randomized study of 420 patients undergoing ovarian stimulation for IVF/intracytoplasmic sperm injection (ICSI), 17 patients (4%) developed moderate to severe ovarian hyperstimulation syndrome (OHSS). Re-evaluation for OHSS on day 4 and 6 after oocyte retrieval identified one patient with continuous risk for severe OHSS, resulting in cancellation of the transfer (1/17, 5.8%). Prospectively, two of three patients had the zona pellucida of the blastocyst removed by pronase exposure prior to transfer. Significantly more patients became pregnant when a zona-free blastocyst was transferred in comparison to transfer of a single zona-intact embryo (9/11 or 82% versus 1/5 or 20%; P < 0.01). Higher ongoing singleton pregnancy rates were obtained when the zona pellucida was removed prior to the transfer (6/11 and 1/5 respectively). This preliminary prospective randomized study indicates that by prolonging the evaluation time for patients at risk of developing OHSS for up to 6 days after the oocyte retrieval, those patients at risk for developing severe OHSS can be identified. Transferring a single zona-free day 5 embryo (blastocyst) and freezing of the supernumerary embryos offers the patient with moderate OHSS an optimal chance for a singleton pregnancy, while avoiding the serious maternal complications of ovarian hyperstimulation syndrome.

Monozygotic twins following blastocyst transfer: a report of two cases

Several studies have shown an increased risk for monozygotic twinning after fertilization treatments. We present the clinical and sonographic characteristics of two monozygotic twin cases following blastocyst transfer. It is suggested that delayed transfer of the embryo in the blastocyst stage is a contributing factor to monozygotic twinning.