If you're going through IVF — or just curious about how it works — you've probably wondered whether it's possible to choose the sex of your baby in the process. It's one of the most searched questions in fertility, and the answer depends a lot on where you are in the world.

In the UK, the rules are clear and quite strict. Here's what you need to know.

Is it possible to choose gender with IVF?

Technically, yes — IVF does make it possible to identify the biological sex of an embryo before it's transferred into the uterus. But whether you can act on that information depends entirely on where you live and why you're asking. 

Preimplantation genetic testing (PGT), specifically PGT-A, which screens all 23 chromosome pairs including the sex chromosomes, can identify an embryo's biological sex with very high accuracy. PGT-A is sometimes still called PGS; the older term PGD now refers to tests for specific inherited conditions, PGT-M.

So yes, the technology exists to know the sex of an embryo. But choosing to implant based on gender for personal reasons is a different matter as there are different regulations in different countries. It's worth checking what applies where you live.

How is sex determined in embryos?

Human embryos carry 23 pairs of chromosomes — and one of those pairs determines biological sex. A normal embryo has either two X chromosomes (XX), which is biologically female, or one X and one Y chromosome (XY), which is biologically male.

During IVF, embryos can be tested using PGT before transfer. A small number of cells are removed from the outer layer of each embryo at around day five or six of development. Those cells are analysed in a genetics lab, where all 23 chromosome pairs — including the sex chromosomes — are examined. This is how a clinic is able to identify the biological sex of each embryo before any decision about transfer is made.

How does gender selection with IVF work?

Here's the basic sequence of how sex identification happens during IVF:

1. Eggs are retrieved and fertilised

The IVF process begins with ovarian stimulation, egg retrieval, and fertilisation with sperm in a lab. The resulting embryos are monitored as they develop.

2. Embryos reach the blastocyst stage

Around day five or six of development, embryos reach what's called the blastocyst stage. At this point, an embryologist carefully removes a small number of cells — typically 5 to 10 — from the outer layer of the embryo. This part of the embryo goes on to form the placenta, not the baby itself, which minimises risk to the embryo.

3. Cells are sent for genetic analysis

The cells are sent to a genetics laboratory while the embryo is frozen at the clinic. Results typically come back within 7 to 10 days.

4. Chromosomes are analysed

In the lab, all 23 pairs of chromosomes are examined — including the sex chromosomes. An embryo with two X chromosomes (XX) is biologically female. One with an X and a Y chromosome (XY) is biologically male. This is how the sex of each embryo is identified.

5. An embryo is selected for transfer

Once results are in, the doctor reviews which embryos are chromosomally healthy and, where permitted, which sex they are. The selected embryo is thawed and transferred to the uterus.

When carried out correctly, PGT can identify an embryo's biological sex with very high accuracy.

Can you choose gender with IVF in the UK?

No — not for personal or social reasons.

This is where the UK law is very direct. UK law is clear that selecting the sex of your child for any reason other than preventing serious inherited illness is strictly prohibited.

The body that governs this is the Human Fertilisation and Embryology Authority (HFEA) — the UK's independent regulator of fertility treatment. The HFEA only permits embryo sex determination if it is needed to avoid passing on a serious medical condition linked to a specific sex.1

The Human Fertilisation and Embryology Act 2008 put a ban on sex selection of offspring for non-medical reasons into statute, having previously been HFEA policy. Sex selection is allowed for medical reasons, for example, to avoid a serious disease that affects only males.2

In simple terms: if you want to choose a boy or a girl because of personal preference, that is not permitted at any licensed UK fertility clinic.

When is sex selection allowed in the UK?

Sex selection is permitted in the UK only for medical reasons — specifically to avoid passing on a serious sex-linked genetic condition to a child.

Some genetic conditions only affect (or predominantly affect) one sex. In these cases, a couple at risk of passing on the condition may be allowed to use PGD/PGT to select an embryo of the sex that would not be affected. This is a clinical decision, not a personal one, and requires the involvement and approval of a licensed clinic and often a genetics specialist.

Examples of conditions where this may apply include certain X-linked disorders, where a mutation on the X chromosome leads to illness in male children.

Why does the UK restrict gender selection?

The UK's decision to restrict gender selection reflects a cautious approach to reproductive technology. The concern with non-medical sex selection includes potential societal consequences, including skewed sex ratios and questions about whether personal preference should determine which embryos are created and discarded. The HFEA has consulted publicly on this issue and has consistently maintained that the ban on social sex selection should remain in place.

IVF success rates

Success rates are one of the most important — and most misunderstood — things to look at when considering IVF. They vary quite a bit, and age is the single biggest factor.

According to the HFEA, the average overall pregnancy rate from IVF using fresh embryo transfers and a patient's own eggs increased from 22% per embryo transferred in 2013 to 31% in 2023. That's a meaningful improvement, driven by advances in lab technique and embryo selection.

Here's how the numbers break down by age group (pregnancy rate per fresh embryo transferred, 2023):3

• Under 35: 41%

• 35–37: 34%

• 38–39: 25%

Rates continue to decline with age above 39. For patients aged 43–44, the pregnancy rate per embryo transferred is significantly lower. This is why the HFEA and fertility specialists consistently emphasise that earlier treatment, where possible, tends to give better outcomes.

It's also worth knowing that a single IVF cycle doesn't always result in a pregnancy. Many people go through more than one cycle, and success rates are quoted per embryo transferred — not per full round of treatment. The HFEA's patient-facing guidance notes that one cycle of IVF can take 3 to 6 weeks.4

The overall picture is encouraging. IVF treatment is more successful now than at any point in its history — but it's not a guaranteed outcome for anyone, and the honest answer is that results vary from person to person.

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Sources:

1. (HFEA) — Statement on sex selection

2. (HFEA) — Fertility law needs modernising

3. (HFEA) — Fertility Treatment Trends and Figures 

4. (HFEA) — Key facts and statistics