As Jennifer Aniston shares IVF journey, how does the fertility treatment work and who's eligible?

Jennifer Aniston speaking out about her "challenging" journey with in vitro fertilisation (IVF) to try and get pregnant has helped to shine a light on the experience of many women.

The actor, 53, revealed that she secretly went through the process several years ago, admitting: "I was trying to get pregnant. It was a challenging road for me, the baby-making road".

"I was going through IVF, drinking Chinese teas, you name it," she told Allure. "I was throwing everything at it. I would’ve given anything if someone had said to me, ‘Freeze your eggs. Do yourself a favor.’ You just don’t think it. So here I am today. The ship has sailed."

But how exactly does IVF work and who can have it?

Read more: More than a quarter of under 35s considering freezing sperm or eggs to future-proof their fertility

What is IVF?

IVF is one method that can help with having a baby if you have fertility problems. During the process, an egg is removed from the woman's ovaries and fertilised with sperm in a lab.

Once fertilised, the egg is called an embryo, and is returned to the womb to grow and develop, just as with a normal pregnancy. It can either be carried out using your own eggs and your partner's sperm, or with eggs and sperm from donors.

This is different to egg freezing, when they aren't mixed with sperm, but instead stored to be used in the future. Freezing healthy sperm or eggs while young can increase the chances of successful fertility treatment.

What happens during IVF?

If you are having difficulty getting pregnant, your first port of call is to speak to your GP, who can advise on how to potentially improve your chances. But if this doesn't work, they can refer you to a fertility specialist for treatments such as IVF.

The process has six main stages, which include, as per the NHS:

1. Suppressing your natural cycle

Your natural menstrual cycle is suppressed with medicine, to make other medicines used in the next stage of the process more effective.

This is done either via an injection that you'll be taught to give yourself every day, or as a nasal spray, continuing for around two weeks.

2. Helping your ovaries produce more eggs

You'll next be given a fertility hormone called follicle stimulating hormone (FSH) to help your ovaries produce more than one egg at a time. This is with the aim of collecting and fertilising more eggs, increasing the choice of embryos to use in your treatment.

3. Monitoring your progress and 'maturing' your eggs

The development of your eggs will be checked with vaginal ultrasound scans, and sometimes blood tests. Before they are collected, you'll have an injection of another hormone called human chorionic gonadotrophin (hCG) to help them mature (ripen, ready to be fertilised, in a sense).

4. Collecting eggs

Your eggs will be collected with a needle passed through your vagina and into each ovary, with the help of an ultrasound, taking around 15 to 20 minutes.

You'll be sedated during the collection, but might experience cramps or a small amount of vaginal bleeding afterwards.

5. Fertilising eggs

This is when the eggs are mixed with the sperm in a lab to fertilise them. Sometimes, each egg might need to be injected individually with a single sperm, called intra-cytoplasmic sperm injection or ICSI.

The embryos will then continue to grow in the lab for up to six days before being transferred into the womb, with one or two of the best chosen.

You'll have been given hormone medicines to help prepare the lining of the womb to receive the embryo.

6. Transferring embryos

When the embryos are placed into your womb, this will be done with a thin tube called a catheter, passed into your vagina.

The procedure is more similar to having a cervical screening, or smear test, and you won't need to be sedated. The number of embryos that will be transferred should have been decided before starting treatment, which can be dependent on your age and which IVF cycle you're in.

If any suitable embryos are left over, they can be frozen for other attempts.

After embryo transferral, you should wait around two weeks to have a pregnancy test to see if it has worked.

Read more: Fertility experts debunk the most common myths around conceiving

Who's eligible for IVF?

The National Institute for Health and Care Excellence (NICE) fertility guidelines has recommendations for who should be offered IVF, including women under 43 who have tried to get pregnant naturally for two years.

That said, the final decision about who can have NHS-funded IVF in England is down to local integrated care boards (ICBs), with it possible for their criteria to be more strict.

For those who find they aren't eligible and have no option but to pay for treatment, you can have it at a private clinic, typically costing up to £5000 or more for one cycle.

Lesbian women can also choose to have IVF, with the option of 'co-IVF', which means eggs are extracted from one woman, fertilised with a donor sperm, and then transferred back into the other woman's uterus for pregnancy.

In July, the government announced plans to remove additional barriers to IVF for same-sex couples, stating: "There will no longer be a requirement for them to pay for artificial insemination to prove their fertility status and NHS treatment for female same-sex couples will start with six cycles of artificial insemination, prior to accessing IVF services, if necessary."

There are also options for trans people to have IVF, who may choose to preserve their fertility before having hormonal therapy or reconstructive surgery.

Read more: Major breakthrough on fertility treatment for lesbian couples

The chances of success of IVF depends on age, and the cause of infertility if known, with younger women more likely to be successful and those over 42 not usually recommended due to low chances. While it is possible and a great option for some, in many cases it is also unsuccessful, and you might wish to wait a couple months before trying again, as it can be a difficult emotional journey.

There are risks of IVF to consider too, including side effects from medicine, multiple births and other complications. See the NHS website for more information.

NICE also recommends counselling should be offered before, during and after IVF, regardless of outcome to help you understand the implications of treatment and provide support at difficult times. This type of talking therapy will allow you to confidentially discuss your problems and feelings.

IVF can be a challenge both physically and mentally, but there is help and support out there if you need it.

You can also contact the Fertility Network UK on Monday, Wednesday and Friday on 0121 323 5025 or at support@fertilitynetworkuk.org, or on Tuesday and Thursday on 07816 086694 or at janet@fertilitynetworkuk.org, between 10am and 4pm.

Watch: 50-year-old explains why she had an IVF baby alone