Sex selection technique 80 percent effective

A new technique for selecting sperm during assisted reproduction appears to produce embryos of a desired sex with 80 percent accuracy.

The research took place in the USA where it is legal for parents having IVF to select the sex of their child. The sperm were sorted by weight, as the X chromosome is larger than the Y chromosome, meaning that X-bearing sperm are, on average, heavier than those containing a Y. While this sperm sorting technique appears safe and effective, the study has raised long-standing ethical concerns surrounding embryo sex selection.

Study leader, Professor Gianpiero Palermo, from Weil Cornell Medicine in New York described the technique as 'extremely safe as well as efficient, inexpensive, and ethically palatable.'

'The sperm [in the study group] moved well, and the sorting technique didn't impair sperm in any shape or form', he said.

The study, published in PLOS One, involved 1317 couples who were having IVF, of whom 105 wanted a child of a particular sex.

For those couples, the sperm sorting technique was used, and then in all cases, the collected eggs were fertilised using ICSI. There were no significant differences between the couples who used sorted or unsorted sperm in terms of fertilisation or pregnancy rates. All embryos in both groups underwent PGT-A, which was also used to determine the sex of the embryos.

For the couples who wanted a girl, 79 percent of their embryos were XX, and for those who wanted a boy 80 percent were XY. The 29 children born as a result have been followed up for three years so far and are healthy and developmentally normal.

Ascertaining an embryo's sex by PGT-A is close to 100 percent accurate and US couples can already use this to choose the sex of the embryo transferred. However, the new technique can give them more embryos of their desired sex from a single round of egg collection.

Attitudes to sex selection vary around the globe, and in the UK its use is strictly limited to preventing transmission of gender-specific inherited diseases.

'At present, in the UK, it is not permitted to choose the sex of a child for non-medical reasons', said Sarah Norcross, director of PET. She added, 'there was a loophole in the 1990 legislation that originally governed this area, but this loophole was closed in 2008.'

However, while embryo sex selection remains controversial, there may be some indications that attitudes are changing according to research conducted last year by Ipsos, and commissioned by PET (see BioNews 1148).

'Overall, permitting sex selection was opposed by 57 percent of the UK public, and was supported by only 28 percent', said Norcross. However, among 16- to 24-year-olds, half supported sex selection.