Choosing the sex of a baby is closer to reality after the successful trials of a technique for sorting human sperm, scientists announced yesterday.
The process can identify and sort sperm into the two types that determine whether a fertilised egg develops into a male or a female embryo. American doctors who are conducting trials on the process said it could be used to "balance" families as well as avoiding potentially lethal diseases such as haemophilia and muscular dystrophy, that boys are more likely to develop.
The doctors have successfully used the "sex sorter" to determine the gender of more than 190 babies born so far, mostly to American parents requesting either a daughter or son to balance the sexual make-up of their families.
Choosing the sex of a baby for non-medical reasons is viewed as ethically unacceptable in Britain and has been outlawed by the Human Fertilisation and Embryology Authority, even though many British parents have requested help in choosing the gender of a baby to balance their families.
The breakthrough relies on a machine called MicroSort, which counts individual sperm cells with speed and accuracy. It works by distinguishing sperm carrying an X chromosome – which results in female embryos – from male-determining sperm carrying a Y chromosome. The two sperm are normally produced in a 50:50 ratio. The technique was originally invented in Britain and "tags" chromosomes with a fluorescent marker. Sperm that carry the X chromosome are more fluorescent because they have slightly more DNA than the Y chromosome.
The scientists said the machine has also been used to enrich semen with sperm carrying an X chromosome to a point where the percentage has increased from the normal 50 per cent to a maximum of 87.2 per cent. The enrichment is less successful with Y chromosome sperm, achieving a maximum of 72 per cent.
Some scientists have questioned whether it is safe to use on humans because it uses a substance that binds to DNA and may cause deformities. The American team, however, says it has not detected any greater proportion of birth defects than in the general population, although about 500 births would be needed before the measure could be more accurately defined.
Dr Harvey Stern, who led the team from the Genetics and IVF Institute in Fairfax, Virginia, told the European Society of Human Reproduction and Embryology's annual meeting in the Swiss city of Lausanne that the sex sorter has been used to try to determine the sex of 284 embryos created by in vitro fertilisation (IVF). He said it successfully determined the sex of 255 of these embryos -- a success rate of 90 per cent. Of these, 190 have been born.
He said: "Gender selection remains controversial but [some commentators] on both sides of the Atlantic suggested that for family variety and balance, this is not unethical. I think this is not a terrible thing."
"Some people want daughters to put them in little dresses. I have a gentleman with vineyards who wanted a son to leave them to. I don't have an ethical problem with that. I look at it fairly simply. I want to help couples have the healthy children they want," he said.
"MicroSort is currently still undergoing clinical trial, but we already know it substantially increases the chance of a couple having a child of a particular gender," he added.
"Another important factor is that it may result in sufficient embryos for one or more frozen embryo transfer cycles as well, which means the woman may be able to avoid having to undergo additional IVF cycles if the first transfer is unsuccessful."
Old Wives' Tales
* In the 18th century men who wanted to father boys were advised to have their left testicle removed.
* Victorian couples went on a strict diet because it was widely accepted that males were the "starved sex."
* American men are told to wear tight underwear if they want a girl and drink coffee before sex if they want a boy.
* In Italy, the man bites his wife's right ear if he wants a son, her left ear if he wants a daughter.Reuse content