Why it's harder to fall pregnant as we get older: A doctor explains.

Females are born with their lifetime supply of eggs, which naturally declines gradually in quantity and quality from the age of 25, becoming almost non-existent by the time of menopause.

Therefore, as a woman’s age increases, her fertility decreases, particularly after the age of 35, due to this diminishing egg reserve.

The dilemma is that the average age for Australian women having children continues to increase and is currently 30.1, compared with about 25 in the early 1970s. This delay in having children appears to be primarily due to women choosing to pursue careers, travel and other matters first.

The consequence, however, is that with this increase in maternal age, more women than in previous generations are experiencing fertility issues, often due to their declining ovarian (egg) reserve.

While some medical issues can impact on fertility, by far the biggest factor affecting conception rates now is age.

What are the conception rates by age?

Conception rates for normal, healthy couples are, at best, 20-25 per cent per menstrual cycle. Once a woman reaches the age of 35, her fertility begins to decline.

By age 40, it is estimated that a female’s natural conception rate is in the range of 8-10 per cent a month and at age 43, the pregnancy rate is thought to be as low as one-three per cent a month.

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In addition to this reduction in pregnancy rates associated with increasing female age, statistically there is a significant increase in the risk of miscarriage and chromosomal (genetic) abnormalities.

Of course, my best advice is to not put off starting a family until it is too late, as the stress that it can create can be significant for some. However, for many reading this, age is probably already marching on.

What can be done?

For those who are already concerned about their chances of conceiving, there is a common way to check a woman’s egg reserve: the anti-Mullerian Hormone (AMH) levels test.

The AMH test, or as some dub it the “egg timer” test, measures the blood’s AMH levels, which reflect the number of small follicles present in a woman’s ovaries. These follicles enable reproduction by ensuring monthly ovulation (release of eggs).

Low levels of AMH in the blood, in conjunction with a number of other tests, are indicative of poor ovarian reserve and in many cases are therefore useful as a marker of fertility.

However, it is important to note that many women who have low AMH levels still fall pregnant. It is therefore essential for this test to be ordered by gynaecologists and fertility specialists, who are trained to interpret the results and explain them in detail.

When should I seek advice?

The general rule of thumb is to seek fertility advice from a specialist if you are having trouble conceiving and have not achieved a pregnancy after 12 months (or six months if you are over 35) of unprotected intercourse.

Once a thorough investigation has been undertaken to try to determine the cause of the fertility issues, there are several options that can assist with conception, ranging from advice to ovulation induction techniques and, if nothing else has helped, medically appropriate IVF methods.

Doctor Shiri Dutt is a specialist at City Fertility Centre, Gold Coast.