What are the methods for selecting sex in the baby?

The selection of the sex of the future baby is a controversial issue regarding the use of assisted reproduction techniques.

Scientifically, it is possible to choose the gender of the future child with specific methods thanks to advances in fertility treatments. However, this does not imply any advantage in terms of getting a pregnancy and is the reason why this practice is not allowed in Spain.

In our country, only the choice of sex is legal with the aim of avoiding hereditary diseases linked to sex. In contrast, in other countries such as the USA, this technique is routinely used for family balance.

Below you have an index with all the points that we will discuss in this article.

Index

What are the methods for selecting sex in the baby?

1. What is the selection of sex?
2. Pre-embryonic techniques
2.1. Microsort
2.2. Ericsson method
2.3. Shettles method
2.4. Whelan method
3. Post-embryonic technique: the DGP
4. Questions from users
4.1. What is done with embryos that we do not want after PGD?
4.2. Why is the choice of the baby's sex not allowed in Spain?
4.3. What diseases can be avoided with the selection of sex for therapeutic purposes?
5. Recommended reading

What is the selection of sex?

The development of the male or female gender in an embryo after fertilization is determined by the genetic material of the sperm provided by the father. The spermatozoa can be carriers of both the X chromosome and the Y chromosome. In this sense we can find two assumptions:

Sperm with X chromosome: the offspring will be a girl.
Sperm with Y chromosome: the offspring will be a male.

The selection of sex consists of manipulating one of the initial stages of fertilization or embryonic development to have a child with the desired male or female gender.

The stages in which assisted reproduction can interfere to achieve this goal are the following:

Preconceptional or preembryonic stage: sperm is chosen before fertilization.
Post-embryonic stage: the desired embryo is selected after fertilization to transfer it to the uterus.
Postconceptional stage: voluntary arrest of the pregnancy if the baby is of the unwanted sex.

For ethical reasons, the voluntary detention of pregnancy is not a good technique for choosing the gender of the future child. However, a woman is free to abort if she so desires of her own free will.

Techniques for choosing sex

Pre-embryonic techniques

As we have already said, these methods consist of selecting the sperm with X or Y chromosome according to the desired sex.

The advantage they have is that it is not necessary to create embryos that can not be used afterwards. However, they are not very effective and their use in fertility clinics is decreasing.

Here are some options:

Microsort

It is a high-tech technique based on the content of the genetic material within the sperm.

The Y chromosome is much smaller than the X chromosome. Therefore, the male sperm has 2.8% less DNA inside it than the female sperm.

The apparatus designed to identify this difference and classify the sperm is called a flow cytometer and the technique is known as Microsort.

Once the sperm carrying the X chromosome have been separated from the carriers of the Y chromosome, they can be introduced into the female reproductive system by artificial insemination (AI) to achieve pregnancy.

The success rate of the Microsort is 70-80%. However, this procedure is still being tested in clinical trials and does not yet have the approval of the United States Food and Drug Administration (FDA). The reason is the use of a dye to separate the sperm that could affect the posterior viability.

Ericsson method

The basis of this technique is the speed of sperm swimming.

Due to the DNA content of the sperm, it is said that the carriers of the Y chromosome will be lighter and faster than the carriers of the X chromosome, which will be slower.

With a modification in the semen training protocol in the laboratory, it is possible to enrich the sample with the sperm of the desired sex and introduce them directly into the uterus through an AI.

The success rate of the Ericsson method is around 70%.

Baby sex selection

Shettles method

It consists of scheduling sexual relations on specific days of the woman's menstrual cycle.

The defenders of the method Shettles support the issue that the sperm carrying the Y chromosome are faster and live less than carriers of the X chromosome. Therefore, during the days close to ovulation there will be more chances of having a male. In contrast, about four or five days before ovulation the possibility of having a girl increases because the sperm with the X chromosome survive more days.

To know when ovulation takes place, the method of body temperature measurement can be used.

Some of the specialists who are in favor of this theory point out that its reliability is 75%, but other experts question it.

Whelan method

It also consists in scheduling sexual relations based on ovulation. However, this theory contradicts the previous one.

The Whelan method states that the biochemical changes that favor sperm with the Y chromosome occur first in the woman's cycle. So, if you want to have a child, intercourse should occur between four and six days before ovulation and, on the contrary, if the desire is to have a girl, it is best two or three days before ovulating.

The effectiveness of this method is questioned as in the previous case, although some claim that it is 60%.

Post-embryonic technique: the DGP

The acronym DGP corresponds to preimplantation genetic diagnosis, which takes place once the embryos are obtained in the laboratory during an in vitro fertilization treatment (IVF).

The main application of PGD is to select a "genetically healthy" embryo to avoid having a child with a genetic disorder. In addition, as this technique allows to analyze all the chromosomes of the embryo, it is possible to observe the existence of the X or Y chromosome and know the sex of each one.

DGP for sex selection

After doing this genetic analysis, the chosen embryos are transferred to the uterus of the mother in order to achieve pregnancy.

Its effectiveness for the selection of sex is 100%. To avoid diseases or genetic alterations it is also highly effective. However, any future mother over the age of 35 is advised to perform amniocentesis during pregnancy to rule out genetic abnormalities.

Questions from users

What is done with embryos that we do not want after PGD?

If PGD results in an embryo with genetic alterations, it is discarded because it would result in a non-viable pregnancy or a newborn with some disease. In the case of sex selection, the resulting embryos with the unwanted sex can be donated to another couple who need the adoption of embryos to be parents or donate them for research purposes.

Why is the choice of the baby's sex not allowed in Spain?

Because Law 14/2006 qualifies the selection of sex or genetic manipulation for non-therapeutic purposes as a very serious infraction, whose penalty ranges from ? 10,000 to a million euros.

What diseases can be avoided with the selection of sex for therapeutic purposes?

Recessive diseases linked to the X chromosome such as the following: Duchenne muscular dystrophy, hemophilia, color blindness, X-fragile syndrome, etc.

It is also possible to avoid diseases linked to the Y chromosome such as, for example, microdeletions that cause azoospermia.

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