When does your biological clock really start ticking?

We’ve spoken to top fertility experts to give you the low down on fertility

When it comes to fertility, British women are becoming first time mums later and later in life, with the birth of Prince George highlighting this trend.

While Kate Middleton, at 31, was in no way old, she was still over a decade older than Princess Diana was when she gave birth to Prince William. Things have changed a lot in a generation and the number of first-time UK mothers in their 40s has risen by 15% in the last five years.

But at what age do we actually need to start worrying about having kids from a biological perspective? While lots of women are able to conceive later on, could some of us be at risk of missing our chance to become a mother if we wait for too long?

What age does your fertility start to decline?

‘There is no ‘magic number’ at which female fertility declines but we know that eggs deteriorate with age,’ says Infertility Network UK’s deputy chief executive Susan Seenan.

‘The speed of that deterioration will vary but rises more steeply after the age of about 35. The more “fertility aware” you are the better, so you can make an informed decision and be aware that it might take you longer to conceive,’ she adds. You could try using a fertility calculator to better track your chances of conception.

The NHS agrees that 35 is a key age when it comes to female fertility. Women are most fertile in their early 20s and their fertility declines with age. From the age of 35, this fall becomes steeper.

‘Women in the 19-26 age group have double the chance of conceiving each menstrual cycle compared with 35-39-year olds,’ explains Fertility UK fertility nurse specialist Jane Knight.

Women over 35 are also less likely to become pregnant from treatments like IVF, and are more likely to suffer from miscarriages.

So does this mean that we all need to get pregnant by 35 or risk never being able to have kids? Not necessarily. You may want to start worrying when you reach 37, though. ‘Egg quality diminishes significantly from about 37,’ explains Jane.


Speak to your mum

Your personal danger age could also be down to genetics. Fertility expert Zita West suggests looking at your mum. ‘One important question to ask is at what age your mother had the menopause as this may be the same for you,’ she says. ‘The decline occurs when the quality of the eggs is diminished with age, and this is usually in the late thirties to early forties.’

But just because you’re still having periods, it doesn’t mean that you’ll get pregnant easily. ‘Nature plays a cruel trick in that women tend to go on having periods long after they have ceased to ovulate,’ says Jane.

‘The ovulation mechanism becomes faulty and the egg quality is very poor long before a woman reaches her menopause, and a woman may no longer be fertile for up to ten years before she has her last period. The average age for menopause is about 51, but many women will have a much earlier menopause.’

Fertility test

It’s probably best to find out for sure by getting tested. ‘Each woman is different when it comes to fertility and we can now use blood tests and ultrasound scans to see the fertility potential by looking at egg reserves,’ explains Zita. ‘The more egg reserves you have the better your fertility, however this won’t tell us about the quality of the eggs,’ she warns.

One of the biggest issues with getting pregnant later on is that your eggs could be damaged. ‘Older eggs are likely to be chromosomally abnormal, especially if you are in your forties,’ says Zita.

It will also take longer to conceive as you age. ‘On average, it can take up to a year to conceive so you need to look ahead and start earlier bearing this in mind,’ she adds. ‘And the older you are, the greater the chance of having other factors that will hinder conception too.’

According to the NHS, around one third of couples in which the woman is over 35 will experience fertility problems, and this rises to two-thirds when the woman is over 40. But that still means that lots of women in the 35+ age bracket are getting pregnant easily.

The best things you can do to try to protect your fertility and prolong your chances of conceiving later on are getting checked regularly for STIs (chlamydia and gonorrhoea can damage your fallopian tubes), maintaining a healthy weight, drinking sensibly and avoiding smoking.


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