Fertility, pregnancy and the biological clock

If you’re hoping to become pregnant this year and are concerned about your biological clock, then Dr Thomas Mathews, Medical Director at Bourn Hall Clinic, has some comforting news.

Dr Thomas MathewsHe says:  “For the vast majority of women, fears of infertility are unfounded. In the general population 70 percent of couples will conceive naturally within 18 months of trying for a baby and 90 percent within two years. If you’re hoping to become pregnant this year, then Dr Thomas Mathews, Medical Director at Bourn Hall Clinic, has some comforting news.


“Contrary to popular opinion, the proportion of couples experiencing fertility problems has remained relatively constant since the first surveys in the 1980s.  Here, at Bourn Hall, we have also seen no evidence that sperm counts are falling.”

But fertility does decline with age. For a woman in her 20s the natural pregnancy rate per month is 20-25%.  Once she is over 35 the chance of becoming pregnant each month falls to 10%.

Dr Mathews says that many women are still unaware of the sudden drop in fertility at 35 and its implications.

AMH test – a biological clock test?

A few years ago there was much hype about ‘Biological Clock Tests’ that claim to predict future fertility based on a measurement of AMH (anti-Mullerian hormone) to assess ovarian reserve.

He says: “The AMH test is useful as it allows us to calculate the amount of fertility drugs a patient may require. However, it can only tell us a woman’s fertility today and does not indicate how a woman’s fertility will change over time. The danger with these tests is that a woman may think that if her fertility is fine today, she can safely put off having children. She may be devastated to find that in just a couple of years she has become sub-fertile and has difficulty conceiving.”

However, the good news is that IVF success rates are increasing.

“Our most recent figures show that over 50% of women up to the age of 38 are becoming pregnant following treatment at Bourn Hall and this is higher than the natural pregnancy rate,” says Dr Mathews. “The increasing use of blastocyst culture, where embryos are grown for longer before transfer to the patient, is improving success rates especially in the over 35s.”

“Couples can do much to boost their natural fertility by improving their general health and fitness.  Losing weight, stopping smoking and reducing alcohol intake are all sensible measures anyway but crucially important when you want to conceive,” he says.

“On our website, you can find ten top tips to help enhance your natural fertility. If becoming pregnant does prove to be difficult for you and your partner, then showing that you are aware of these measures and have acted upon them will help your GP to agree the next steps with you.”

More information

Our top ten tips to improve your fertility.

If you are still concerned about your fertility our Fertility Health + Wellbeing Test can help you to understand your options.

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