Choosing the baby’s sex may be easier and more affordable thanks to a new technique developed by researchers at the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine at Weill Cornell University of Medicine in New York. The researchers, led by Gianpiero D. Palermo, one of the pioneers in assisted reproduction credited with discovering the ICSI or sperm microinjectionhave tested a new technique to select spermatozoa in 1,317 couples who were undergoing fertility treatment and, with this, increase the chances that the embryo will be of one sex or the other. What is new compared to other approaches is that the proven efficacy is around 80%.. The results are published in the journal “PLoS ONE”.
The technique, he explains to ABC Salud Palermo, consists of placing the sperm sample “on multilayer density gradients of variable concentrations in a tube, and then letting the spermatozoa swim through the layers to “self-select”.” This solution, he adds, «routinely used in fertility clinics around the world and unlike some previously tested sperm sex selection techniques, extraneous factors are not used in this method.”
In other words, explains Marta Martínez Sáez, the embryologist in charge of the Ginemed Málaga Laboratory, the method makes it possible to select the spermatozoa that will provide the X (female chromosome) or the Y (masculine) using a multigradient technique. “In other words, it would allow the sex of the embryos to be selected in assisted reproduction laboratories.”
The method of sex selection, new and safepoints out Palermo, is capable of diverting the proportion of spermatozoa towards the desired sex in couples.
The risks, clarifies Palermo, “are more theoretical than real.”
Thus, he explains that “they are inherent to sperm selection itself, since the selection of sperm for a specific sex is carried out based on the weight of the sperm head, which could include not only female sperm, but also aneuploidies (chromosomal abnormalities) . However -he clarifies-, the data presented in this article did not indicate a higher incidence of aneuploidy in sperm or conceptus (product of conception at any point between fertilization and birth)”.
To test safety, the researchers followed the children up to 3 years and 6 months of age and found that “his psychological and motor development was within the normal range», clarifies Palermo.
For Rocío Núñez Calonge, embryologist, scientific director of the UR International Group, in statements to the Science Media Center, the novelty is that two groups have been evaluated using preimplantation genetic diagnosis (PGT-A) to study chromosomal abnormalities in the resulting embryos, and in one of the two groups to use the sperm selection technique that they propose. In this way, “they compare between the two groups whether the sperm selection technique for a given sex is useful and safe and no more chromosomal abnormalities are found after its use.”
The results of the study confirm that a certain sex can be selected with an 80% probability and safely, since the technique, which is very simple, does not affect the genetic load of the embryo.
wrong embryo
The authors acknowledge a limitation: the sex of the embryo chosen for transfer is not known.. “Although our sperm sex selection method does not necessarily guarantee offspring of a specific sex, the couples participating in the study were nonetheless able to obtain a higher proportion of desired sperm,” the researchers write.
But it can happen that, among several embryos obtained, although the majority are of the sex that has been wanted to obtain, the wrong one is chosen. «Despite the demonstrated efficacy -they write-, on rare occasions all the embryos analyzed were of the opposite sex to the one selected. This can be attributed to subtle morphological and functional differences between X- and Y-bearing sperm after selection.”
The results of the study confirm that a certain sex can be selected with an 80% probability and safely
“These encouraging results indicate that our method is not only effective but also safe, making it a feasible and ethically acceptable procedure,” the scientists conclude.
And Palermo adds that because it is a very simple method, very similar to that carried out in the preparation of semen in laboratories, it can be very useful in assisted reproduction centers for couples who wish to increase the probability to obtain a child of the desired sex.
But at the same time that the results are encouraging, acknowledges Martínez Sáez, «sin turn recklesssince in the future the sex of the baby could be chosen, which can generate many ethical problems ».
Although some countries such as the US allow this type of procedure, currently the selection of sex in the field of assisted human reproduction is prohibited in Spain and in many other countries, adds Martínez Sáez. “It is only allowed to select the sex of the embryos in the case of hereditary disease linked to sex.”
However, the researchers say that sperm selection is more ethically acceptable than embryo selection.
Spain and in many other countries, it is only allowed to select the sex of the embryos in the case of hereditary disease linked to sex
The authors propose that this technique can be used both for couples who want to select the sex of the baby out of personal desire and for medical reasons when there is a sex-linked disease, and that this would be more ethical than using PGT (preimplantation genetic testing).
For Núñez Calonge, professor in the Master’s Degree in Reproduction at the Complutense University and the Spanish Fertility Society, from a purely medical point of view, the use of this technique when there are sex-linked diseases (such as hemophilia), does not would be appropriate, since an 80% probability leaves the couple a 20% chance that the baby will not be of the chosen sex, giving rise to a person with the disease. However, if the selection is solely for personal reasons, this margin of error would be acceptable.
Solution to select sperm
For this reason, it does not seem to resolve the possible ethical problems that the use of the PGT already raises in this regard.
When the law was made in 1988, this issue was raised based on the possible selection that certain groups could make to the detriment of the other sex and that would lead to an imbalance in the population, recalls Núñez Calonge. «Currently this prohibition does not make much sensesince the selection of sex would be carried out by a small group of patients for personal reasons, and would not imply a population imbalance».