Preimplantation genetic diagnosis (PGD) and genetic testing for aneuploidy (PGT-A): status and future challenges.

The world's first in vitro fertilization (IVF) baby was born in July 1978 in the UK. Since then, more than 7 million infants have been born worldwide as a result of IVF. Preimplantation genetic diagnosis (PGD) was introduced in the late 1980s for couples at risk of transmitting a genetic abnormality to their children. From the mid-1990s, this technology has been employed as an embryo selection tool for patients undergoing IVF and has been known as preimplantation genetic screening (PGS). The aim of this practice has been to identify and select euploid embryos for transfer, in order to increase efficacy of IVF cycle, ensure higher implantation rates or at least decreased time to pregnancy. In the early days, fluorescent in situ hybridization (FISH) technology was used for genetic analysis. New advancements in both biopsy and cytogenetic have made possible the improvement of PGD and PGT-A analysis. Currently, a variety of technologies have been implemented to individuate euploid embryos to be preferentially transferred in IVF treatments. The purpose of this review is to clarify the differences between PGD and PGT-A, and to discuss current indications and requirements for embryo biopsy and genetic methodologies used.

In vitro fertilisation (IVF) with donor eggs in post-menopausal women: are there differences in pregnancy outcomes in women with premature ovarian failure (POF) compared with women with physiological age-related menopause?

PURPOSE: This study assessed pregnancy rates and obstetric outcomes in women with premature ovarian failure (Group A) with post-menopausal women > or =40 years (Group B) who had IVF +/- ICSI using donor eggs. METHODS: This was a retrospective analysis of 54 recipients with either premature ovarian failure or physiological menopause undergoing oocyte donation between 2000 and 2007 at Monash IVF. RESULTS: The average number of stimulated cycles required for a woman in group A and B to deliver a baby was 1.75 and 1.4 respectively. Both groups had high cumulative pregnancy rates; however, there was a statistically significant difference with regards to rates of complications. CONCLUSION: Oocyte donation in both premature ovarian failure and physiological menopause is highly successful and cumulative pregnancy rate is an important statistic which can be used to inform women seeking this technique. High rates of complications, in conjunction with individual risk-factor analysis needs to be considered when counselling post-menopausal women about oocyte donation.

Blastocyst transfer does not cause a sex-ratio imbalance.

OBJECTIVE: To determine whether either single or double fresh blastocyst transfers result in a sex-ratio imbalance in resulting offspring compared with transfers on day 2 or 3 and whether there is a correlation between rate of embryo development and sex of the embryo. DESIGN: Retrospective analysis. SETTING: Large IVF center. PATIENT(S): Four hundred thirty-five live births from single fresh ETs for the period January 2005 through July 2007 and 2,043 live births from double ETs for the same period. INTERVENTION(S): Statistical analysis performed on sex ratio of offspring resulting from transfers (day 2, day 3, day 4, and blastocyst), as well as on the stage of development reached for each day in culture analyzed on sex of the embryo. MAIN OUTCOME MEASURE(S): Sex ratio of offspring by day of transfer. Stage of embryonic development by sex for each day in culture. RESULT(S): There was no difference in sex ratio with blastocyst transfer (single or double). There was no difference in speed of embryonic development at any stage in vitro. CONCLUSION(S): Male embryos do not grow faster than female embryos in culture. Blastocyst transfer does not result in a sex-ratio imbalance in resulting offspring.

Is there an ideal stimulation regimen for IVF for poor responders and does it change with age?

PURPOSE: To determine whether there is a superior treatment modality for 'poor' responders. METHOD: Retrospective analysis of three stimulation regimens, with patients stratified based on age, stimulation regime and response in previous cycles ("poor' responder or "non poor" responder). Fertilisation, embryo utilisation and clinical pregnancy rates were assessed. There were a total of 1,608 cycles in the 'poor' responder and 8,489 cycles in the 'non poor' responder groups. RESULTS: In 'poor' responders there was no significant difference in fertilisation rate, nor utilisation rate between the three stimulation regimes and no differences in the pregnancy rate/initiated cycle irrespective of age and stimulation regimen in any of the groups. 'Non poor' responders had a significantly greater pregnancy rate/initiated cycle for all stimulation regimens in both age groups compared with 'poor' responders. CONCLUSION: This large retrospective study of 'poor' responders has not shown a difference in pregnancy rates/initiated cycle between stimulation regimens.

Elective transfer of single fresh blastocysts and later transfer of cryostored blastocysts reduces the twin pregnancy rate and can improve the in vitro fertilization live birth rate in younger women.

OBJECTIVE: To determine the extent to which embryo selection by blastulation and elective single blastocyst transfer, supported by efficient cryostorage of spare embryos, can reduce multiple pregnancies and maintain or improve on the live birth rate from IVF. DESIGN: Prospective, nonrandomized cohort study. SETTING: Sydney IVF, a private clinic in Australia. PATIENT(S): In vitro fertilization patients aged <38 years with three or more usable blastocyst, recruited from April 2000 through December 2001, with pregnancies followed up until August 2004. INTERVENTION(S): Blastocysts were cultured and cryostored with stage-specific culture medium and low oxygen conditions. MAIN OUTCOME MEASURE(S): Fetal heart-positive twin pregnancy rate and accumulating "take-home baby" rate per retrieval leading to blastocyst transfer. RESULT(S): Among 121 women who elected single fresh blastocyst transfer (but who could elect to have two frozen blastocysts transferred at once), 79 (65.3%) took home a baby, with a twin pregnancy rate of 7%. Among 285 women who chose two blastocysts for fresh transfer, 184 (64.2%) took home at least one baby, with a twin pregnancy rate of 34% and five perinatal deaths. CONCLUSION(S): With technically appropriate blastocyst culture and freezing, and elective single blastocyst transfer in the fresh cycle, the overall multiple pregnancy rate can be reduced by >75%, permitting in this series a slight increase in the chance of taking home a baby.

Moving to blastocyst biopsy for preimplantation genetic diagnosis and single embryo transfer at Sydney IVF.

Developments at Sydney IVF in the successful culture of blastocysts, combined with day 5 or 6 blastocyst biopsy and blastocyst cryostorage after biopsy, permit up to five or six cells to be genetically tested, leaving the inner cell mass intact and enabling embryos to be electively transferred one at a time. These advantages can be obtained without diminishing the chance of pregnancy compared with cleavage-stage biopsy and testing.

Single embryo transfer in IVF to prevent multiple pregnancies.

As the success rates of IVF clinics improve, one of the adverse consequences is the increased incidence of twins, due largely to the number of embryos transferred. Even if the number of embryos transferred is restricted to two, the twinning rate can exceed 40% of the pregnancies. An obvious way to reduce this high twin rate would be to transfer only one embryo. This would require that cryopreservation of the supernumerary embryos be efficacious enough so that the chance of achieving an ongoing pregnancy is not diminished by transferring a single embryo in the stimulated cycle. Previous studies utilising embryos on day 2 and 3 of development have shown that the pregnancy rates can be acceptable (about 40%) and that the cumulative rate can be up to 60%. Most of these studies, however, do not include a comparison with the cumulative pregnancy rate with two embryos transferred in the stimulated cycle. Therefore, the efficacy has not been proven. We present clinical data from the past few years to illustrate the increase in success rates and the concomitant increase in twinning rates. The increased success in the cryopreservation program has enabled us to trial a single embryo transfer program and compare the results to the transfer of two embryos. The results strongly suggest that the transfer of a single embryo is the better clinical option.