1. Is there a right time to have a baby?

A much older woman having a baby still raises headlines across the world, but over the last few decades there has been a dramatic increase in the age at which women decide to have children, with the oldest in the UK 66. But how old is too old?

For women who decide to have children, the ability to freeze eggs reliably means they may choose to wait until their career is fully established, they are financially secure, have time to spend with children – or are with their dream partner.

As clinicians we recognise that the risk of pregnancy complications increases enormously as women age. So rather than just thinking of egg freezing as another option, it raises the new question: Am I too old to have children?

2. Pregnancy around the world

The worldwide average age that women become first-time mothers.

The worldwide average age that women become first-time mothers ranges from 18 to 30. Today, women from more affluent countries are having their first babies much later, with British first-time mums in the top 30 oldest in the world. The youngest are in Angola, Bangladesh, Niger, Chad, Mali, Guinea, Uganda, Mozambique and Mulawi, where the average age is 18 years old.

3. Babies on ice

The average life expectancy for women in the UK is now 83, but most women are infertile from around 45. When you consider that a woman could freeze her eggs when she is 25, that they can stay frozen indefinitely without harm, and on use give her the same chance as if she was only 25 years old, this enables a completely new paradigm for choosing when to have your family. Scroll through the gallery to discover the journey of a frozen egg.

Women are born with a finite number of eggs (oocytes) and don't make any new ones in their lifetime. As they get older, their egg cells decline in number, and by 30 only about 12% remain.

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As women mature, there is also an age related decline in egg cell quality that can drive the reduction in fertility and an increase in miscarriage.

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In order to get the eggs required, the fertility clinic will stimulate your ovaries with hormones for two weeks and then retrieve them. To retrieve the eggs, a needle is passed through the vaginal wall into the follicles.

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Here a doctor performs a follicle puncture to harvest human eggs. Even with large egg numbers, the live birth rate from just one cycle is limited. Multiple egg freezing cycles are likely to be required to give a high chance of future success.

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Eggs are then frozen using a process called vitrification. This is a more advanced ultra rapid cooling technique than the original method of freezing, and lessens the risk of possible damage to the genetic material from ice crystal formation.

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With advances in freezing technology, frozen eggs are now almost as good as fresh eggs. However the process is still very new - statistics are scarce as very few women have retrieved their eggs,

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Eggs can be stored for long periods of time – initially 10 years in the UK, with a further extension possible. Once cryogenically frozen, an egg will age just a single second over 10,000 years.

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Once a woman decides to attempt pregnancy – maybe months or years later – the eggs are thawed, injected with a single spermatozoon and left in an incubator to fertilise. After two to five days the embryos are transferred into the uterus.

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The chance of having a live birth from frozen eggs depends on how many are stored, the age of the woman when she stored them and how they were frozen.

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Vitrification (freezing eggs) provides no guarantee that you will one day have a baby, but the younger you are when freezing your eggs, the more likely they are to be viable.

4. Hard to conceive

If women use their eggs when they feel the time is right for them to have children, no longer will biology limit when they can have a family.

But as clinicians we recognise that the risk of pregnancy complications increases dramatically as women age, and that young families may be left motherless. So although women in their seventies in other countries have had babies, is this right and should we limit the age at which we can use eggs?

Even from the relative young age of 34, the chances of success with IVF decrease from ~30% by ~3% per year. By the time women are in their 40s the use of donor eggs from a younger woman provides the only realistic hope for many of having a family with IVF.

At present there is no universal agreement, with clinicians and professional bodies required to guide patients on the risk and set their own age limits for treatment. Freezing eggs may enable a prolonged reproductive lifespan, but there is inevitably a balance for women and society in the optimal time to have a family.