Table of Contents

Introduction (sex selection) 1

Pre-Implantation methods. 2

Post-Implantation methods. 3

Post-birth methods 4

Legality 4

Ethical concerns 4

Demographic concerns 5

History and beliefs 5

Conclusion 5

Bibliography 5

It’s a lively Friday night, and my phone is constantly going off. Eventually, I gravitate towards a specific conversation that is intriguing me more than ten or so other conversations.

In this chat, I am trying to argue the “fact” that males “naturally” decide the gender of an offspring. My friend, on the other hand, points out that men don’t determine which sperm chromosome makes it to the ovary first. He continues to explain that, men release about 100 million sperms in ejaculation and after that, the fastest sperm gets to fertilise the ovary. This concludingly establishes that neither parent “naturally” determines the sex of their child. However, this makes me question whether there are factors that determine which sperm chromosome fertilises the ovary and mainly if these are factors that we can control. As I dive into finding the answers to all my questions, I decide to make a blog, and here I am now, giving you all my findings on sex selection in my first article.

Introduction (sex selection)

Typically, sex and gender are confused for the other. Sex is either the activity of sexual intercourse or the two main categories into which humans and most living things are categorised based on their reproductive functions (1). The latter will be the centre of our interest in this article. Gender, on the other hand, is either two of the sexes, especially when considered concerning social and cultural differences rather than biological ones. More broadly, gender extends to refer to the range of identities that do not correspond to established ideas of male and female (2). These identities are most commonly referred to as the L.G.B.T.Q.I.A.+. Community.

Naturally, when a male and female human being have sexual intercourse with the aim of conceiving, upon ejaculation, semen with X and Y sex chromosomes will be released into the cervix of the female. If she is in her fertile window, the fastest sperm that makes it to her ovary will facilitate fertilisation, and there will be a 50% chance of either conceiving a male or female baby. The human ovary has two XX chromosomes, and depending on which chromosome from the semen makes it to the ovary first, the female will either conceive a male or female offspring. If an X sperm makes it to the ovary first, a female child will be the result, and if a Y sperm makes it to the ovary first, a male child will result of this fusion.

There a few factors that determine which sperm chromosome is likely to make it to the ovary first, and these are dominantly structural differences. The Y sperm chromosome is smaller in size, which makes it lighter and therefore, a speedier swimmer. This advantage gives it a higher chance of making it to the egg first (3). However, the X sperm chromosome which is denser and slower is more resilient and will last for longer, long after the Y chromosome has died off which could give it a chance to make it to the ovary in time for fertilisation to occur (4). The structural differences between the Y and X sperm chromosomes present the X sperm chromosome at a natural disadvantage which might explain why there are more boys than girls born each year. According to BBC News, not in one year since Queen Victoria’s reign has the number of newly born girls outnumbered that of boys in England and Wales (5).

What’s next if you have been trying for a girl or a boy and you seem to be hitting a dead end? (6) Sex selection helps to broaden and maximise your 50% chance of conceiving preferred sex. Sex selection refers to the practice of using medical techniques to choose the sex of offspring (7). Methods of sex selection are categorised based off of when the choice is made. These include Pre-implantation methods, Post-implantation and Post-birth methods. The safest and least controversial are the Pre-implantation methods (8). Two primary pre-implantation methods are used for sex selection, and they are, The Ericsson method and the IVF/PGD technique. Both these methods are based on choosing the second sex chromosome to either be a Y or X chromosome.

Pre-Implantation methods.

The Ericsson Method involves using a high concentration of the desired sperm chromosome to increase the likelihood of conceiving the preferred sex. The high sperm concentration is made by passing sperms through the blood protein, serum albumin. When the sperms pass through the protein, the difference in mass between the X and Y chromosome leads the lighter Y chromosome sperms to float and the X to sink deeper into the protein hence creating separate layers. These layers are not pure, and this explains the 25% chance of gender selection failure associated with this method (23). This method was first applied clinically in 1970 by Doctor Ronald J. Ericsson. In cases where such a technique is used to increase chances of having a female child, studies show that this has yielded a 70% – 80% successful outcome while when used to increase chances of having a male child, it has been 50% – 75% successful. At the moment, around 50 gender selection centres in the US use the Ericsson Method for preimplantation gender selection.

On the other hand, the IVF (In-vitro fertilisation) / PGD (Preimplantation Genetic Diagnosis) involves removing eggs from a female after ovarian stimulation and then fertilising then in a laboratory using the male’s sperm in a technique called “In vitro” (Latin for “within the glass”) fertilisation. As the embryos develop, they are separated, and the desired sex is implanted in the mother’s uterus. This technique is favoured over the Ericsson method because there is more control of the offspring’s sex in the laboratory and also because only the embryo of the desired sex is transferred into the mother.

Timing Methods are a popular subsection of preimplantation sex selection, and they aim to affect the ratio of the offsprings by having sexual intercourse at a specific time with relation to ovulation. Research about whether timing methods influence the sex of the baby has not been consistent, but these are worth a try and will probably not cost as much as other pre-implantation methods. The Shettles Method, which was first theorised by Landrum B. (24) Shettles in the 1960s and is based on the theory that X sperm chromosomes are more resilient than Y sperm chromosomes. This method recommends sexual intercourse 2 – 4 days prior to ovulation so that by the time ovulation occurs, most of the Y sperm chromosomes have died off leaving a higher concentration of X sperm chromosomes. However, if the aim is to try for a male child then having sexual intercourse closer to ovulation should increase the chances of conceiving one since the Y sperm chromosome is a faster swimmer.

Another known intercourse timing method is the Whelan method, and this is quite the opposite of the Shettles as it advocates having sexual intercourse 4-6 days prior to ovulation to increase the chance of the egg being fertilised by a Y chromosome sperm.

A relatively newer timing method is The Baby Dust method which was modelled by Kathryn Taylor (9). This method was created after Leonie McSweeney’s 2011 study (10) in which 99 Nigerian couples participated. The aim of Leonie’s research was to test whether the sex of an offspring can be determined by timing intercourse in relation to ovulation just like most timing methods. Participating couples were required to monitor their ovulation and then having sexual intercourse in consistent with the timing and frequency associated with the sex of the child they preferred. Ovulation was determined by the Peak symptom in regards to the Billings Method (11). The Billings Method is a form of birth control that seeks to teach women how to recognise their fertility patterns and then to relay of the conception of their cervical mucus to decide when to avoid sex or when to initiate it. Throughout the menstrual cycle, cervical mucus changes in predictable ways as it often becomes clear and elastic about 6 days prior to ovulation as a result of the effect of oestrogen. Post ovulation, cervical mucus becomes thick, sticky and opaque. Leonie’s study had the couples that wanted to conceive a male child use the Post-Peak approach and for couples that wanted a female child, the Pre-Peak approach was used. These approaches were used after four months of keeping track of the cervical mucus patterns of each female involved. The study resulted in a 94.9% success with 78 of 81 trying for a male (96.3%) successful and 16 of 18 seeking for a female (88.9%) successful.

Both Taylor and Leonie’s methods recommend intercourse once 2-3 days before ovulation for a girl and twice as close to ovulation as one can for a boy. However, according to Kathryn Taylor, creator of the Baby Dust Method, cervical mucus naturally differs from woman to woman and therefore can vary depending on the location of their cervix, and other factors like breastfeeding, antibiotics, prior hormonal birth control and fertility medications like Clomid. The Baby Dust Method fundamentals consider this by having women chart their luteinising hormone twice a day for a minimum of three months before attempting to conceive as this would help them to recognise their cycle patterns (12).

The luteinising hormone usually peaks 24 hours before ovulation, so testing at least twice a day is paramount. The morning test is particularly important as you have been holding your urine for the longest time. Another test should be done in the evening before you go to bed because testing once a day might lead you to record your luteinising hormone surge later than it actually happened or you might even miss it totally. Luteinising hormone is tested using ovulation strips, and you need to be able to see the slight changes in the darkness of your result line to be able to predict ovulation for sex-selection. Taylor had her pre-planned baby boy in 2012 and a pre-planned baby girl in 2014. She later realised her book, The Babydust Method: A Guide to Conceiving a Girl or a Boy in 2016 (13).

Finally, sperm sorting is another popular preimplantation sex selection method. This is an advanced technique that sorts sperm “in vitro” by flow cytometry where a laser is shone over sperms to distinguish their chromosomes and automatically separate them into X and Y chromosome samples (14). Doctor Glenn Spaulding was the first to use viable whole human and animal spermatozoa using cytometry, and this was during the early and mid-1980s. Before flow cytometry is done, a fluorescent dye which sticks to the DNA of each spermatozoon is used to distinguish the sperms. Since the X chromosomes are more substantial and therefore has more DNA than the Y chromosome, it will absorb more dye than the Y chromosome. Due to this, when they are exposed to UV light, the X chromosome spermatozoa fluoresce more than the Y. As the spermatozoa go through the flow cytometer in a line, each one of them is enclosed in by a droplet of liquid and assigned an electric charge depending on its chromosome. X chromosomes have a positive charge while Y chromosomes have a negative charge. The streams of X and Y droplets are then separated by means of electrostatic deflection and collected in different collection tubes.

Several other methods can be used for sex selection, but these have no scientific research backing them yet. However, if you are really longing to try them out, you still have a 50% chance either way (15). One of these methods is to stick to less penetrating sex positions like the missionary position if you are trying a female child. This is because the depth of penetration restricts how close to the cervix the sperms are ejaculated and therefore the more resilient X chromosome sperms will have a higher chance of making it to the egg before the Y chromosomes. On the other hand, if you are trying for a male child, deep penetration is probably more ideal. Another method that one could work for sex selection is to avoid the female orgasm if the aim is to try for a female baby. The female orgasm releases an alkaline secretion that helps sperm cells to survive longer, which means that Y chromosome sperms will thrive even more in such an environment. Without these secretions, the Y chromosome may find it harder to survive, so the more resilient X chromosome might make it to the egg first.

Post-Implantation methods.

The second major category of sex selection is Post-implantation, and this can be performed by prenatal sex discernment which is then followed by sex-selective abortion of offspring of the unwanted sex. Prenatal sex discernment is a test whose goal is to find the sex of a foetus before birth (16). This can be done before a pre-implantation genetic diagnosis before conception, but it isn’t always classed as prenatal sex discernment because it can be performed even before implantation. Methods of prenatal sex discernment include cell-free foetal DNA testing where a venipuncture is executed on the mother to analyse the small amount of foetal DNA that can be found within it (17). This can be done in the 7th week of pregnancy (earliest post-implantation test).

Other methods of prenatal sex discernment are Chorionic villus sampling (CVS) and Amniocentesis. These are quite invasive procedures, and this makes them rare during the first trimester and more commonly done after the 11th and 15th week of pregnancy. CVS and Amniocentesis are considered invasive because they risk injury to the foetus, congenital abnormalities and might result in miscarriages too. CVS is a prenatal diagnosis used to determine chromosomal or genetic disorders in the foetus. It involves the sampling of the chorionic villus (placenta tissue) and testing it for abnormalities (18). Amniocentesis, on the other hand, uses amniotic fluid as a sample to examine genetic abnormalities (19).

A more standard procedure of sex discernment is Obstetric ultrasonography also known as Prenatal ultrasound. This test can provide information like the health of both the mother and foetus. Information about the timing and progress of the pregnancy can be obtained from this test as well. Prenatal ultrasound tests check for the sagittal sign as a marker for foetal sex either transabdominal or transvaginal between 65-69 days from fertilisation, and it gives an accurate result in almost 100% of the times (20).

Reasons for prenatal sex discernment usually include diseases testing, preparation for any sex-dependent aspects of parenting and sex selection. When it is done for disease testing or sex selection, sex-selective abortion might be performed depending on the test results and personal preference. A 2006 survey found that 42% of IVF clinics in the USA provide PGD as a sex selection method but for non-medical reasons, and this is usually for family balancing. However, half of these clinics do not restrict sex selection to family balancing.

Post-birth methods

Finally, the most controversial sex selection category is Post-birth selection. These methods include sex-selective infanticide, where children of unwanted sex are killed off. Killing off children of the adverse sex is illegal in most countries, but it is still practised. Another post-birth sex selection method is sex-selective child abandonment, and this involves abandoning children of unwanted sex which is illegal too in most parts of the world. Sex-selective adoption is also a post-birth sex selection method, and this is where parents put up children of unwanted sex for adoption. However, families adopting children and have a gender preference can choose offspring of a specific sex through legal means.

The medical reasons that might lead to engaging in sex selection include preventing the birth of children that are or might be affected by X-linked disorders. Low fertility rate makes it almost impossible for couples to conceive, and this is, in turn, increases the need for sex selection since they are usually offered the chance to select embryos for transfer and implantation. This is often the final step following the process of sperm sorting during In Vitro Fertilisation (IVF). Non-medical reasons include family balancing reasons where a couple wants a particular sex because they have one or more of another sex. Other non-medical sex preference reasons often stem from cultural, social and economic bias.


A significant range of ethical, social, moral, demographic and legal implications arise from sex selection practices as you can imagine, especially if it is done for non-medical reasons. Sex selection is judicial in most parts of the world however the Pre-implantation genetic diagnosis which a potential expansion of IVF and can be used for sex selection, is prohibited in the UK, Canada and Australia except when it is used to screen for genetic diseases, but laws on this subject are more relaxed in the US. Sex selection is illegal in China and India, but the practise is still widespread. Prenatal sex discernment by ultrasound is against the law in India and this was strengthened further by an amendment in 2003 due to rampant sex-selective abortion, but this is still being practised in the more rural areas.

Ethical concerns

In regard to the ethicality of sex-selection, providers have argued that this technology is an expression of reproductive rights and was initiated and pursued by women as a way of female empowerment that minimises intimate partner violence. It is also argued that this technology allows couples to make well-informed family planning decisions, prevent unwanted pregnancies, abortion and child neglect. Physicians question whether women can genuinely express free choice under pressure from family and society and are concerned that sex selection has led to invasive interventions in the absence of therapeutic indications. This, in turn, contributes to gender stereotypes and can easily lead to child neglect. The Ethics Committee of the American Society of Reproductive Medicine concluded that sex selection is ethically appropriate when it isn’t used for non-medical reasons. Any other ideas would be morally inappropriate; however, methods like PGD involve use of preferred embryos and pregnancy termination for gender selection which raises ethical concerns for the abortion debate.

Demographic concerns

With this in consideration, demographic issues rise mainly for communities where social sex selection is rampant. A society might have high favouritism for specific sex due to either economic or cultural concerns, and this could lead to a significant sex imbalance. This has been observed in several nations mainly in the Far East like India and China, where sex selection has led to unnaturally high male to female ratios hence a larger male population. China’s one-child policy has further increased the gender imbalance mainly in most urban communities as the government ratio shows a rate of boys to girls as 118:100, and this is higher in rural areas. Such areas like Guangdong and Hainan have a boy to girl ratio of 130:100 compared to a rate of 104:100 in developed Western countries, and this is believed to keep increasing. A lot of social problems will arise from this as mates will get scarce, there will be a high demand for prostitution, mass emigration might follow suit and so might selling of brides. On the other hand, Western countries have shown no particular preference for particular sex; thus, no significant sex imbalance (21).

History and beliefs

Despite all the speculation, sex selection is not a new practice. A French author of the book, The Art of Boys from the 18th century suggests that each testicle and ovary are intended for each sex respectively so by removing a testicle or ovary, the other sex is guaranteed. In ancient China, the Chinese used the Chinese Gender Chart to predict or select the baby’s sex, and this has a history of over 300 years. This sex chat matched the day of conception of the future child with the age of the mother at the day of understanding was based on Yin-Yang, Five Elements, Eight Diagrams and time. The table contains one more chance to conceive a boy, and this might reflect the current female to male ratio. These ancient ideologies and practices among many more others show you how far sex selection has come.


The progression of sex selection methods makes me wonder what the future of sex selection is going to look like. Methods like IVF and sperm sorting have broad potential. Developments in IVF allow targeted genome editing, which allows all sorts of possibilities like stopping the transfer of genetic disorders. This creates hope for discovering a cure for certain cancers and other diseases. However, this also means that couples can choose cosmetic traits of their offspring, thus creating what is referred to as “designer babies”. Ornamental features that can be chosen include eye colour, hair colour and the like. Eventually, people might have the option to choose or predict more advanced traits like certain behaviours, intelligence or even athletic capabilities.

It’s both exciting and scary how this could develop in the nearby future (22).


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