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expert reaction to US study looking at safety and effectiveness of new sperm sex selection technique in couples undergoing ICSI IVF cycles

A study published in PLOS ONE looks at the safety and efficacy of a novel sperm sex selection technique.


Comment on the public perception of sex selection for non medical reasons and the legal framework in the UK):

Sarah Norcross, Director of PET, said:

“Research commissioned by PET last year – conducted by Ipsos – asked whether people undergoing privately funded fertility treatment in the UK should be able to choose the biological sex of their child (for non-medical reasons).

“Overall, permitting sex selection was opposed by 57% of the UK public, and was supported by only 28%. However, there was an interesting and statistically significant generational divide.

“Younger age bands were more likely to support people being able to choose the biological sex of their child. For example, 50% of the UK public aged 16-24 supported the permitting of sex selection, and only 35% within this age band opposed the permitting of sex selection.

“At present, in the UK, it is not permitted to choose the sex of a child for non-medical reasons. There was a loophole in the 1990 legislation that originally governed this area, but this loophole was closed in 2008.’

 ‘Fertility, Genomics and Embryo Research: Public Attitudes and Understanding’, Progress Educational Trust, June 2022, p11. Ipsos interviewed a sample of 2,233 adults aged 16-75 in UK using its online i:omnibus between 24 and 27 March 2022. Data has been weighted to the known offline population proportions for age, working status and social grade within gender and Government office region.


Prof Darren Griffin, Professor of Genetics, University of Kent, said:

“The issue of sex selection is an ethically fraught one. Selection of embryos on the basis of sex, without mitigating reason such as sex-linked disease, is illegal. Separating sperm beforehand may provide a legal loophole in some countries but not the UK.

“There have been numerous methods around for decades, some effective but potentially harmful, others dubious in their effectiveness.  The current paper seems to have found a method in which the approach is effective to some degree.  It involves separation on the basis of density and the difference in this study compared to previous ones I have seen is that it performs industry standard tests on the sperm and on the embryos.

“I am convinced that the science is sound and that, instead of the usual 50:50 “coin toss” then a couple can get a baby with the desired sex a little under 80% of the time.  There exists an issue here however with the management of expectation.  Does the procedure warrant the benefits that the 4 out of 5 couples who will get what they want compared to the added disappointment that the 1 out of 5 that do not?  Should we selecting for sex anyway rather than letting nature take its course?”


Dr Channa Jayasena, Head of Andrology, Imperial College London, said:

“The authors selected sperm based on whether they contained an X chromosome (making female offspring) or a Y chromosome (making male offspring).  The results show convincingly that this technique is able to select sperm to determine the sex of embryos made using those sperm.  However, their technical achievement is insignificant compared to the serious ethical concerns raised by the research.  The authors clearly describe the understandable ethical concerns of embryo selection and abortion of pregnancies based on (usually female) sex.  However, they propose sperm selection as an ‘ethical’ alternative to embryo selection.  I find this incredible since sperm selection is just another way of selecting embryos to manipulate the sex of offspring, with detrimental societal implications.

“I am alarmed that such technology might become more widespread in clinical practice.  Currently, it is prohibited in the UK to select offspring unless they have a serious medical problem.  I would be interested to learn whether the technique described in this study contravenes UK regulations.  Though not described in the study, their technique might be adapted in the future to select for other bodily traits such as sperm containing a gene affecting skin or eye colour.  This research therefore raises serious ethical concerns which need to be addressed urgently through regulation.”


Comment sent out by our colleagues at SMC Spain:

Rocío Núñez Calonge, embryologist, scientific director of the UR International Group and lecturer in the Master’s Degree in Reproduction at the Complutense University of Madrid and the Spanish Fertility Society, says:

“This study on a new sperm sex selection technique is written by one of the leading pioneers in assisted reproduction, Professor Palermo, who is credited with the discovery of ICSI or sperm microinjection. It is a well-designed study, with a high number of cases, of good scientific quality. The journal [in which it appears] does not publish papers that are not of high quality.

“At first, this did not seem to me to be a very novel topic since, as the authors themselves point out, there are many previous studies on the same subject. The novelty lies in [separating] two groups using preimplantation genetic diagnosis (PGT-A) to study chromosomal abnormalities in the resulting embryos, and in one of the two groups using the proposed sperm selection technique. In this way, the researchers compare the two groups to see whether the sex-specific sperm selection technique is useful and safe, and whether further chromosomal abnormalities are found after its use.

“The results of the study confirm that it is possible to select a particular sex with a 80% probability, and safely–since the technique, which is very simple, does not affect the genetic load of the embryo.

“The authors propose that this technique could be used both for couples who want to select the sex of the baby out of personal desire and for medical reasons–that is, when there is a risk of disease linked to the sex of the baby. They say this would be more ethical than using pre-implantation genetic testing.

“From a purely medical point of view, the use of this technique when there is a sex-linked disease (such as haemophilia) would not be appropriate, as an 80% chance leaves the couple with a 20% chance that the baby will not be of the chosen sex, resulting in a person with the disease. However, if the selection is made purely for personal reasons, this margin of error would be acceptable.

“In addition, the authors themselves speak of an important limitation, which is that the sex of the embryo chosen for transfer is not known. It may happen that, among several embryos obtained, although most of them are of the desired sex, the wrong one is chosen. From an ethical point of view, what happens to the rest of the embryos that are not chosen? What would be their fate?

Therefore, it does not seem to solve the possible ethical problems that the use of PGT raises.

“In Spain, sex selection is not allowed except for medical reasons. When the law was passed in 1988, this issue was raised on the basis of the possible selection that certain groups could make to the detriment of the other sex, which would lead to an imbalance in the population.

“At present, such a ban does not make much sense, as sex selection would be performed by a small group of patients for personal reasons, and would not lead to a population imbalance.

“The use of the technique proposed by the authors could be very useful in assisted reproduction centres, as it is very simple (almost the same as what is usually done for the preparation of sperm in laboratories), and could help couples who wish to increase the probability of obtaining a child of the desired sex. However, it is only an increase in this probability. [Couples] should be well informed beforehand and not offered any certainties.”



‘A non-randomized clinical trial to determine the safety and efficacy of a novel sperm sex selection technique’ by Stephanie Cheung et al. was published in PLOS ONE at 18:00 UK time on Wednesday 22 March 2023.

DOI: 10.1371/journal.pone.0282216



Declared interests

Sarah Norcross: PET – is a charity which improves choices for people affected by infertility and genetic conditions.

Prof Darren Griffin: “He has published extensively on sexing in sperm and IVF embryos.  He does not perceive a direct conflict of interest but has links with companies that may have a tenuous one e.g. Care Fertility, London Women’s Clinic, Conceivable, Cooper Surgical and Igenomix.”

Dr Channa Jayasena: “None.”

Rocío Núñez Calonge: declared no conflicts of interest.


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