Editorial: “Designer babies are on the horizon but aren’t here yet“
CONNOR, a healthy baby boy, has made history. He is the first child to be born after his parents had the entire genomes of a batch of their IVF embryos screened for abnormalities, with the intention of picking the healthiest for implantation.
The technique could increase the number of successful pregnancies from IVF. And although the researchers stopped short of sequencing the boy’s genome, the advance is proof that this could be done – potentially ushering in an era of designer babies.
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IVF accounts for between 1 and 5 per cent of all births in developed countries, but it is very inefficient. About 80 per cent of embryos either don’t implant or miscarry, largely because of abnormalities in the number of chromosomes an embryo possesses. Only a third of IVF cycles result in a successful pregnancy.
The problem is that many abnormal embryos look normal under a microscope. “We need better ways of working out which embryo is the one that we should implant,” says at the University of Oxford, who pioneered the new technique.
To do this, he first took cells from seven 5-day-old embryos and extracted their DNA. He then used a technique called next-generation sequencing (NGS) to assess the number of chromosomes in each cell. This involves breaking the DNA into fragments, which are then amplified to increase the number of each. These are then read by a computer that predicts where on the chromosome each fragment came from. The sequence of an entire genome can be read in this way – although Wells’s team didn’t do this. They were merely interested in the proportion of DNA coming from each chromosome.
In earlier studies, the team had compared the DNA fragments produced using NGS from healthy cells, those taken from abnormal embryos and those taken from cells with known chromosomal abnormalities. These were used as a library against which the DNA from the seven embryos could be compared.
Of the seven embryos, three were found to be normal, and one was implanted into the mother, resulting in the birth of Connor in Pennsylvania in May (see “The chosen one“).
The hope is that by selecting the healthiest embryos for implantation, more women will have successful pregnancies. Recent clinical trials of a related technique have suggested that NGS could boost the successful implantation rate by a third, while the miscarriage rate could be halved. The technique can also be tweaked to examine mutations in any gene of interest, such as those that cause cystic fibrosis. “It gives us a very powerful tool for pre-implantation genetic diagnosis,” says Stuart Lavery, director of IVF Hammersmith in London.
However, it also raises the potential for misuse. Last year, researchers in the US sequenced the entire genome of an 18-week-old fetus using fragments of fetal DNA in the mother’s blood along with DNA samples from both parents. Wells’s procedure shows that it is possible to do this far earlier. “There is the potential for getting an unprecedented amount of information about an embryo before it’s transferred to the womb,” says Wells, who presented his technique at the annual meeting of the in London this week. “We need to be very careful that this isn’t used for trivial, non-medical reasons.”
“We can get a huge amount of information about an embryo before it is placed in the womb”
Earlier this year, a team led by Manfred Kayser of Erasmus Medical Centre in Rotterdam, the Netherlands, published a paper suggesting that eye and hair colour can be predicted from a DNA sample (Forensic Science International, ), and they are now using such tests to help police identify suspects or victims of crime. The same group is also developing tests to predict the shape of facial features, such as prominent cheekbones or a large nose, and complexion.
“For now, eye and hair colour are the only appearance traits that can be predicted from DNA with any practically useful accuracy,” says Kayser. “Some of the available tests are very sensitive and work from a small number of cells provided that the DNA is not heavily degraded. However, the fact that something is scientifically and technically possible doesn’t necessarily mean that it should be done.”
In the UK, genetic testing of embryos is strictly regulated, but this isn’t the case in other countries such as the US. “At some point in the not-too-distant future, parents will have the technical ability to look at the genome of their embryos and select embryos based on the traits they see, whether those are disease traits, cosmetic traits, behavioural traits, or a boy or a girl,” says Hank Greely, director of the Center for Law and the Biosciences at Stanford University in California.
What’s more, enforcing a worldwide ban on such genetic selection might be unworkable, says Greely. “There are roughly 200 countries in the world. If 199 ban it, that’s a great commercial opportunity for the 200th,” he says.
Even so, Wells thinks there are several reasons why using this technology to create designer babies is unlikely to catch on. The first is that couples only tend to produce a limited number of embryos, and all of them carry their own genetic characteristics.
“Two people who are both 5 foot 2 tall are unlikely to produce a basketball player,” he says. And the more traits a couple tried to select, the more embryos would be eliminated. Pick more than one or two traits, and there may be no more embryos left to choose from. “To go through all the difficulties, expense and uncertainty of an IVF cycle to choose something trivial, I can’t see many people doing it,” Wells says.
Month of conception Matter
Trying for a baby? Be warned: the month you conceive appears to influence your baby’s birth weight and risk of being born prematurely.
Janet Currie and Hannes Schwandt at Princeton University compared more than 1.4 million siblings born in New York City, New Jersey and Pennsylvania between 1994 and 2006. They found a 10 per cent higher rate of prematurity among babies conceived in May compared with other times of the year possibly reflecting a spike in seasonal flu when the women were nearing their due date. “Flu induces women who are close to term to deliver prematurely”, says Currie.
Babies conceived during the summer months also tended to weigh 8 to 9 grams more on average than those conceived at other times of the year, perhaps because women who fall pregnant in summer tend to put on more weight overall than those who conceive in other months (PNAS, ).
The chosen one
Marybeth Scheidts and David Levy didn’t know they would be making medical history when Marybeth went into labour on 18 may. But their son, Connor, weighing 7lb 15oz (3.6 kilograms) at birth, is the first child to be born following a new genetic screening technique that could dramatically boost the success rate of IVF (see main story).
Incredibly, the test was performed before the embryo that Connor came from had been implanted in Marybeth’s uterus.
Marybeth, aged 36, and David, aged 41, had always wanted children.But after five years of trying to conceive without success, they visited a fertility clinic.At first it seemed the problem was David’s low sperm count, but then it emerged that Marybeth’s ovulation was erratic as well.”it was a real blow,” says David. “Seeing other people with children, and not having any issues, it was heart breaking.”
After three failed attempts at intrauterine insemination, the couple tried IVF, which resulted in the creation of 13 embryos. Seven looked normal and usually one would be randomly selected for implantation. However, the family had enrolled on a clinical trial of an embryo screening technique, which revealed that just three of their embryos carried the correct number of chromosomes. Two were frozen and one was implanted
Two weeks later, Marybeth called David and asked if she could meet him for lunch. There, she announced she was pregnant. “It was overwhelming,” says David.
The couple say they are adjusting well to life as a three. “Connor only wakes up when he needs changing or feeding; he’s been smiling for two weeks,” says David
Should they decide to have another child in the future, they say they feel reassured knowing that their two remaining embryos are genetically healthy. They also have a choice of gender – one is male, the other female.
This article appeared in print under the headline “The Earliest Health Test”
