A couple in the US has had the first IVF baby to be born as a result of a new way of screening embryos that promises to increase the success rate of in vitro fertilization (IVF) and bring down the cost of treatment.
The new method, which uses the latest DNA sequencing technology, helps doctors screen embryos created by IVF to find the ones most likely to lead to successful pregnancies. The method is able to spot which embryos have the correct number of chromosomes.
Marybeth Scheidts, 36, gave birth to baby Connor Levy in May, according to a BBC report. She and her husband David Levy, 41, had been trying to conceive naturally for four years and had also tried artificial insemination before opting for IVF.
The successful birth of Connor follows an IVF research collaboration between fertility clinics in Pennsylvania and New York and the University of Oxford in England.
Currently in the UK, embryo screening adds another $3,000-$4,500 (£2,000 to £3,000) to the cost of IVF treatments. The new method should reduce this cost, says Dagan Wells of Oxford University, who led the international research team.
Wells is presenting their work at the European Society of Human Reproduction and Embryology’s Annual meeting in London this week.
In vitro fertilization (IVF) is a process where an egg removed from the mother is fertilized by the father’s sperm outside of the body, in a “test tube”, and then implanted back in the mother. It is a major treatment for infertility where other methods, like artificial insemination, have failed.
But most of the embryos made by IVF do not lead to successful pregnancies, so scientists are always looking for new and better ways to spot which ones should be implanted to maximize the chance of success.
One way to spot a viable embryo is just to watch how it grows during the first few days after fertilization. But this doesn’t show whether it has the correct number of chromosomes. Chromosomes are packets of DNA that contain the genetic code that the embryo inherits from the egg and the sperm.
If the embryo does not have the correct number of chromosomes then it is unlikely to lead to a successful pregnancy, as Wells explains in a statement:
“Many of the embryos produced during infertility treatments have no chance of becoming a baby because they carry lethal genetic abnormalities.”
However, even under a microscope it is not possible to see if the chromosome count is correct.
Next generation or high throughput sequencing is an umbrella term for a group of technological advances that has brought down the cost of DNA and RNA sequencing and revolutionized the study of genomics and molecular biology, producing huge quantities of data that can be used again and again.
Next generation DNA sequencing improves the ability to detect chromosome abnormality and spot which embryos fertilized by IVF have the best chance of producing a successful pregnancy, says Wells:
“Potentially, this should lead to improved IVF success rates and a lower risk of miscarriage.”
Other approaches have shown success in trials but they would be too expensive and out of the reach of most patients. So Wells and colleagues set out to find a more affordable route.
Next-generation DNA sequencing technology used to be expensive, but the cost has come down considerably in recent years and the team believes it will get even cheaper.
Wells says randomized trials done in the last year or so show that most IVF patients would benefit from embryo chromosome screening, and next-generation sequencing “could make chromosome testing more widely available, improving access by cutting the costs”.
However, while next-generation sequencing has been revolutionizing research and practice in many areas, before this study it had not yet been applied to embryo screening. The main reason for this is because it is not easy to use the technology on the DNA of a single cell.
But when testing an embryo that is only a few days old, all you can safely remove without harming it is a single cell.
To overcome this difficulty, Wells and colleagues sequenced DNA from several embryos at the same time, and used chemical “tags” to identify which embryo each bit of DNA came from.
Another part of their approach is they do not read the whole DNA code of each embryo. They limit the sequencing to about 2% of the embryo’s DNA. This is enough to find out if there are enough chromosomes.
In an initial validation study of their DNA sequencing approach, the results showed very high rates of accuracy, says Wells.
In that study they used the new approach to look for known chromosome abnormalities, gene defects and mutations in mitochondrial DNA in lab-grown cells.
They also tested the approach in cells from 45 embryos that had already been tested using another method.
Wells and colleagues then worked with two clinics in the US, Main Line Fertility Clinic in Pennsylvania and the New York University’s fertility clinic in New York City, to help assess chromosomes in embryos made by two couples having IVF treatment.
They screened cells taken from embryos five days after fertilization. This found three embryos with the correct chromosome count for one couple and two for the other couple.
In both cases, implanting the screened embryos resulted in healthy pregnancies, one of which became Connor Levy, born to the couple treated in Pennsylvania.
The other baby is due in a couple of months.
Wells suggests they could take the technology further and use it to check for any serious inherited disorders at the same time as doing the chromosome check.
“Next-generation sequencing provides an unprecedented insight into the biology of embryos,” says Wells.
The team is now planning a randomized clinical trial to confirm the effectiveness of their new approach. Wells says they hope to get it under way later this year, working with the Oxford Fertility Unit and the Lister Fertility Clinic in London.
The study involved industrial partners and received significant support from a partnership between the NHS and the University of Oxford.
Last month, the UK government gave its backing to three-person IVF where babies are created from the DNA of three people.
Written by Catharine Paddock PhD