TRYING TO IMPROVE IVF OUTCOMES: WHAT RESEARCHERS ARE WORKING ON NOW! by Ellen Greenblatt, MD, F.R.C.S.C. - SPRING 2011

TRYING TO IMPROVE IVF OUTCOMES: WHAT RESEARCHERS ARE WORKING ON NOW!

by Ellen Greenblatt, MD, F.R.C.S.C.

Since the birth of the first IVF baby, Louise Brown, in 1978, the use of IVF to help individuals and couples become parents has grown exponentially. In Canada and the US, approximately 1% of all births are the result of IVF or a combination of IVF and ICSI (injection of a single sperm into the egg) while this reaches 4% in some European countries where assisted reproductive technology (ART) is publicly funded. Although the first pregnancy was achieved from a non medicated or ‘natural’ cycle, pregnancy rates markedly improved with the introduction of gonadotropin medications to effect controlled ovarian stimulation (COS). This treatment induces the maturation of multiple oocytes which are then retrieved and fertilized in vitro, leading to a cohort of embryos for transfer to a recipient uterus. Excess good quality embryos can be frozen for transfer at a future date.

Despite numerous advances in ART in the form of stimulation protocols, better culture media to sustain human embryo development, improved incubators and laboratory conditions as well as higher implantation rates (I.R.), the likelihood of a single embryo to result in a viable¹ pregnancy still remains around 30%. To increase pregnancy rates, often more than one embryo is transferred to the uterus. In Canada, based on the 2007 Canadian Assisted Technology Registry (CARTR) data, an average of 2.3 embryos were transferred per fresh cycle, for a clinical² pregnancy rate of 35%, which resulted in a multi-fetal pregnancy rate of 30% that year. Multiple pregnancies are considered highly risky due to the increased incidence of all pregnancy-related complications (hypertension, diabetes, haemorrhage, and caesarean section) for the Mom, as well as risks to the fetus(es) of prematurity, measuring small for dates, intracranial bleeding, breathing problems, developmental delay, cerebral palsy and death. The economic, social and marital stress of parenting multiple infants, particularly if the infants are medically or developmentally compromised, is tremendous. Multiple pregnancy is currently recognized as the most pressing complication of ART worldwide.

The only way to decrease the incidence of multiple births is to transfer only one embryo to the uterus at a time. Most countries that follow this approach have seen a marked decrease in their multiple pregnancy rate from 30-35% to lower than 5% in many cases. In Canada we have our own “experiment” with reducing multiple births by increased implementation of single embryo transfer. Quebec recently released data from the first three months of their funded IVF program, which is tied to a policy of single embryo transfer (SET). Data from Quebec shows that in 2009, prior to the adoption of this program, the pregnancy rate in women of all ages was 42.8%.³ With eSET only being used in 1.6% of the cycles, a multiple birth pregnancy rate of 27.2% resulted.³ The new Quebec program has changed these figures radically. In the first three months of the new program (August-November 2010), although the pregnancy rate went down to 32%, SET was used in 51% of cycles and the multiple pregnancy rate dropped to 3.8%!³ As Quebec now fully funds three cycles and all of a woman’s frozen embryos must be used before she can begin a new cycle, it should be noted that a cumulative pregnancy rate of 75% is expected.

However, in the rest of Canada where the cost of IVF is borne by the patient, it is often difficult to convince patients that accepting a slightly lower pregnancy rate from the fresh embryo transfer of a single embryo is in their best interests. Even though a much lower multiple pregnancy rate would be realized, they may also be faced with a need for additional frozen embryo transfer cycles and additional expenses.

At the present time embryos are evaluated and selected for transfer in the embryology lab, based on morphology. This means that the appearance of the embryo and its developmental rate, assessed daily under a microscope, is the current method for determining embryo quality. Research has shown that although some information about an embryo’s competence (ability to result in a live birth) can be determined by these criteria, they are certainly not perfect. Many embryos that look normal will not implant. Many normal-looking embryos, if tested, will be found to be genetically abnormal, and genetically abnormal embryos usually do not implant, or lead to early miscarriage. Genetically abnormal embryos also rarely lead to a live birth with a genetic abnormality, as nature selects out for this outcome. Although the incidence of chromosomal imbalances is higher in embryos that develop poorly, appearance alone cannot determine genetic normality. Embryo genetic abnormalities increase markedly as the women from whom the oocytes are retrieved and the embryos formed, get older. Research has shown that in younger women, up to 30% of oocytes and embryos produced from COS and IVF are genetically abnormal, and this increases to over 65% in women over 40.

Clinicians are now evaluating whether the use of Preimplantation Genetic Screening (PGS) will improve implantation rates and allow more widespread adoption of eSET by selecting only chromosomally normal embryos for transfer. In PGS, either the oocyte itself or one to several cells of a developing embryo, are removed and tested for chromosome number and balance. Although results are preliminary, this may provide a means to enhance outcomes in IVF. Even perfect-looking embryos that are proven to be genetically normal do not implant 100% of the time. Furthermore, PGS is considered an ”invasive” technique, as the oocyte or embryo must be manipulated and genetic material removed.

Another direction of research that is being investigated in order to improve success with IVF involves the use of laboratory research techniques to probe the “Omics” of the oocyte or embryo. Omics is a shortened form that stands for “Genomics”, “Proteomics” and “Metabolomics”, which are techniques applied to embryology research. These techniques probe the oocyte, its environment or the embryo at several stages of development to try to determine patterns that are associated with “competent” embryos.

1 Genomics:.

Deoxyribonucleic acid (DNA) is the chemical compound that contains the instructions needed to develop and direct the activities of nearly all living organisms. An organism's complete set of DNA is called its genome. Virtually every single cell in the body contains a complete copy of the approximately three billion DNA base pairs, or letters, that make up the human genome.

Genomics assesses the genetic material from clinical material, and determines which genes are activated or suppressed in that material. This is called describing the gene expression patterns (of a cell or group of cells). A genetic pattern or fingerprint is then defined and this can be compared between different sources of material. Researchers are using this technique to probe various forms of biological material produced through the IVF process to try to determine the genetic profile of good quality oocytes and embryos leading to live births, compared with those that do not. Genomic analysis of oocytes and related material, as well as of embryos that have been donated for research, is performed to identify gene expression patterns which may help identify competent embryos. The information is being used to determine what pattern(s) are associated with good quality oocytes and embryos. Moreover, as genes dictate the proteins that are produced, this data can direct the search for which proteins may be secreted and associated with the best oocytes and embryos.

2. Proteinomics

Proteinomics is a technique directed at the product of genes: proteins. Some proteins are secreted from the embryo into the media, and scientists are developing techniques to measure the extremely small concentrations of the proteins that may be found in the media in which embryos are growing. Again, if it is discovered that specific proteins are always found in media from competent embryos leading to pregnancies, it is hoped that a test to measure this in the embryology lab would improve the ability for the embryologist to identify which embryo to select for transfer.

3. Metabolomics

As the embryo develops it consumes and produces tiny amounts of factors known as metabolites. Metabolites include things like glucose (sugars) and pyruvate (a product of glucose breakdown), and amino acids (the building block of proteins). Instruments are now being developed to measure the uptake of these substances from the culture media as well as their secretion into the media. Some studies have suggested that these patterns may be representative of embryo quality. If so, then the embryo media could be tested to help the embryologist select one best embryo.

Finally, in addition to a healthy top-quality embryo, a receptive uterine lining (endometrium) is required for a pregnancy to implant and proceed to a live birth. It is known from natural conception that the endometrium will only allow implantation during a short period of time of approximately 3-4 days, called the “window of implantation”. IVF treatment, due to changes in hormone levels that accompany COS, is thought to perhaps negatively affect endometrial receptivity. Genomics and proteinomics, described above, are some of the techniques being used to try to predict the receptivity of the endometrium when an embryo is placed in the uterine cavity.

In summary, although the “Omic” techniques used in basic research are not quite ready for “prime time” use in the clinical embryology lab, the rapid pace of research that is moving genomics, proteomics and metabolomics to the study of human embryo development and endometrial receptivity, will certainly lead to the improved ability to identify top-quality embryos in the near future. This will foster more ready adoption of SET and significantly decrease the most serious complication of ART, namely, multiple births.

References:

1. A pregnancy is determined to be viable when a fetus is seen to have a beating heart and is visualized in the uterus.

2. A clinical pregnancy is confirmed when evidence of the sac can be seen on an ultrasound screening at some time after five weeks of gestation have elapsed.

3. Press conference of the Canadian Fertility and Andrology Society announcing the results of the first three months of the new Quebec IVF-funding program. Montreal, December 2010.

About the author

Dr. Ellen Greenblatt completed her medical school (McGill University) and Ob/Gyn Residency (University of Western Ontario) before moving on to complete a fellowship in Reproductive Endocrinology and Infertility at the University of California, San Francisco. She is a Fellow of both the Royal College of Surgeons of Canada (Ob/Gyn) and the American Board of Obstetrics and Gynecology (ABOG). Dr. Greenblatt is Medical Director of the Centre for Fertility and Reproductive Health and Head of the Division of Reproductive Endocrinology and Infertility at Mount Sinai Hospita, in Toronto. An Associate Professor in the Department of Obstetrics and Gynaecology at University of Toronto, she is on the Board of the non-profit patient advocacy organization Infertility Awareness Association of Canada (IAAC) and an Editor of IAAC’s quarterly publication Creating Families. Her research interests focus on polycystic ovary syndrome, fertility preservation, and optimizing ART treatments.