A new technique for selecting a baby’s gender appears to be around 80% safe and effective, a study has found.
The researchers used a technique to separate sperm by whether they had an X (female offspring) or Y (male offspring) chromosome.
Sperm with an X chromosome are slightly heavier than those with a Y, research indicates.
However, the study again raised long-standing concerns about the ethics of such a process.
Selecting embryos without reasons such as a sex-linked disease is illegal in many countries.
The experts behind the research, from Weill Cornell Medicine in New York, said their technique was inexpensive and “extremely safe”.
The small study involved 1,317 couples, with 105 men in the group who used the sperm sorting process.
Fifty-nine couples wanted a girl and this resulted in 79.1% (231 of 292) female embryos, with 16 girls born without any abnormalities.
Fifty-six couples wanted a boy and the technique produced 79.6% male embryos (223 out of 280), or 13 healthy male babies.
Professor Gianpiero Palermo, one of the authors, called it “extremely safe, effective, inexpensive and ethically pleasing”.
However, some experts have expressed serious concerns despite the technique’s apparent effectiveness.
Dr Channa Jayasena, head of andrology at Imperial College London, said “their technical achievements pale in comparison to the serious ethical concerns raised by the research”.
“They offer sperm selection as an ‘ethical’ alternative to embryo selection,” he said.
“I find this incredible since sperm selection is just another way of selecting embryos to manipulate the sex of offspring, with detrimental societal implications.”
He said regulation was urgently needed to control these developments, adding that it could be adapted in the future to choose traits such as skin or eye color.
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Darren Griffin, professor of genetics at the University of Kent, also said sex selection was “ethically burdensome”.
“Pre-separation of sperm may be a legal loophole in some countries, but not in the UK,” he said.
“Many methods have been around for decades, some effective but potentially harmful, others whose effectiveness is questionable.
“The current paper appears to have found a method in which the approach is effective to some extent…
“I’m confident the science is sound and that instead of the usual 50/50 ‘heads or tails’ game, a couple can have a baby of their desired gender just under 80% of the time.”
The study is published in the journal PLOS ONE.