A new way of processing embryos during IVF treatment can improve the chances of pregnancy by more than a quarter, The Daily Telegraph today reported.
The story is based on research evaluating a new system for incubating newly fertilised embryos during IVF treatment. The new system is designed to protect the growing bundles of cells from environmental stresses that might affect their development. In conventional systems, the embryos had to be transferred between different devices to perform all the various stages of IVF treatment, but the new system allows a range of functions to be performed in a single sealed unit that regulates the temperature and quality of the air around them. This research found that in the conventional system 30% of embryos successfully developed to the ‘blastocyst stage’, which is seen five or six days after fertilisation, compared with 40% in the new system. The new system was also associated with an increase in clinical pregnancy rates during the period that it was introduced.
The findings are interesting, but they do not add up to an IVF “ breakthrough”, as is suggested by The Daily Telegraph. The new method of incubating embryos sounds promising, but no randomised trial has yet been undertaken into its effectiveness. Further good research is needed to investigate whether it can improve pregnancy and live birth rates.
This method of culturing embryos in a laboratory for five to six days after fertilisation before implantation in the womb is called blastocyst transfer. Transferring the fertilised embryo to the womb two to three days after fertilisation is called embryo transfer.
Where did the story come from?
The study was carried out by researchers from Newcastle Fertility Centre, University Hospital of North Tees, Northumbria University and Newcastle University. It was funded by the Medical Research Council. The study was published in the peer-reviewed journal Public Library of Science (PLoS ONE).
The study’s findings were overplayed by the papers. The Daily Telegraph reported that it could increase pregnancy rates by more than one quarter. This is a measure of relative increase, highlighting that the number of successful pregnancies rose by around 25%. However, it is more useful to look at the ‘absolute’ figures, which describe how many people actually conceived out of all those people that used IVF. The absolute increase in clinical pregnancy rates associated with the new system was actually about 10%, with IVF leading to pregnancy in 32-35% of participants in the years before the new system was introduced, and this figure rising to 45% in the year the new system was introduced.
Also, it is not clear if other improvements in IVF occurred over this period and whether these contributed to the increase in successful pregnancies. The Daily Mail misleadingly reported that the new method gave a 40% greater chance of success.
What kind of research was this?
This research reports on various studies relating to the development of a new system of culturing embryos in the laboratory, designed to improve their viability and, eventually, the chances of successful pregnancy.
The authors point out that culturing embryos for implantation into women typically involves the use of open-fronted microbiological safety cabinets, with standalone incubation chambers. This means embryos may need to be removed from the incubator to check on their development in the safety cabinet. This can expose them to changes in temperature and air quality, as well as chemical contaminants, all of which may disrupt cell processes that are key to development.
To protect embryos from the possible impact of environmental stresses, the researchers developed a new fully enclosed chain of pressure-sealed workstations featuring integrated incubators and built-in microscopes, allowing them to incubate and examine developing embryos all within a single apparatus. The workstations were designed to link to adjacent treatment rooms in which women had their eggs retrieved and embryos implanted. The system is designed to provide a controlled environment from the time eggs are harvested from the woman’s ovary until embryos are transferred to the womb.
What did the research involve?
The authors undertook three pieces of research:
- They compared the temperature and air quality of their new enclosed system and the old open system in three separate laboratory experiments.
- They compared embryo development in the enclosed system with that in the conventional system, using mouse embryos.
- They compared the development of human embryos before and after the installation of the new systems.
They then collected data on patients during the period when the new equipment was being fitted and validated. They used this to compare pregnancy outcomes in three consecutive groups of patients - those who had treatment when conventional open-fronted cabinets were used, those who were treated when a temporary laboratory using conventional equipment was in use and those who were treated when the refurbished laboratory using the new enclosed system was in place. To control for differences between patients, they confined their analysis to couples undergoing their first treatment cycle, in which the woman was 37 years or less and had had 10 egg follicles harvested.
What were the basic results?
In their preliminary research they found that the enclosed system was more successful at maintaining temperature and air quality than the conventional system.
- They found that the proportion of human embryos that had developed to the ‘blastocyst stage’ by day seven was 30% for the open system, compared with 40.1% in the new enclosed system. An embryo is called a blastocyst once it has developed for five to six days after fertilisation.
- They say analysis of 600 embryos revealed that the increased rate of blastocyst formation coincided exactly with the change from the open to the enclosed system.
- They also found that embryos produced in the new system contained significantly more cells and had ‘accelerated development’ compared with those cultivated in the open-fronted system.
- Experiments with mouse embryos cultured in the two systems also showed more embryos developing to the blastocyst stage under the enclosed system than in the conventional system.
- Finally, when they compared groups undergoing treatment at different times they found that those treated in the enclosed system had a clinical pregnancy rate of 45.3%, compared with a rate of 32.2% for those treated when the conventional system was in place. A rate of 35.6% was seen while the temporary laboratory was in use. A clinical pregnancy was defined as a heartbeat on a scan at seven weeks’ gestation.
How did the researchers interpret the results?
The new enclosed system, say the researchers, protects embryos from changes in temperature and air quality and promotes improved development.
The new system of culturing embryos sounds like a promising development but further research involving couples undergoing IVF treatment is required to assess whether it improves pregnancy and live birth rates. In particular, the patient data offered by the researchers were not taken from participants in a controlled trial, which means that many other factors might have affected pregnancy rates.
As the authors point out, improved outcomes over this period might have been due to a general improvement in assisted conception procedures during the period of the study, although they say they tested for this possibility.
This may well prove to be a useful technique for IVF, and the researchers have demonstrated its feasibility. More research with a control group of patients is needed before we can be certain of its benefits and lack of harms.
- Hyslop L, Prathalingam N, Nowak L et al. A Novel Isolator-Based System Promotes Viability of Human Embryos during Laboratory Processing. PLoS ONE 7(2): e31010