14/11/2016 5:56 AM AEDT | Updated 14/11/2016 5:56 AM AEDT

Science Can't Reproduce A Healthy Lifestyle

Human biology is not evolving at the same rate as the society we live in.

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Global reproductive health is in decline, with infertility affecting one in every six couples. Take a glance at the headlines, though, and you might not be inclined to believe that this is true.

Earlier this year, Janet Jackson announced she's to become a mum at 50 and Geri Horner (Halliwell) recently shared the news that she's pregnant at 44. Earlier this year, Daljinder Kaur became one of the world's oldest first-time mothers when she gave birth to her son at the ripe old age of 70.

Reading these news stories, it wouldn't be too far-fetched a belief that women might have fewer fertility worries than ever before in this age of burgeoning biomedical research.

Indeed, thanks to this very research, HIV is no longer a death sentence, vaccination has neutralised some of the deadliest diseases of the 20th century and survival rates for some cancers are finally on the increase.

But the truth is, there's only so far biomedical research can take us when it comes to female reproductive health, and these mature-mum celebrity success stories are far from the norm.

Like it or not, a woman's age is still the single most important factor affecting her fertility. As women age, their fertility declines. And contrary to popular belief, this decline begins decades prior to the onset of menopause, in their early thirties.

By the time a woman reaches her forties, she has a 5 percent chance of becoming pregnant naturally when actively trying. And in women over 45, even with the aid of IVF, this rate drops to 1.2 percent.

Women have a finite supply of eggs that exist within each ovary -- this is termed the 'ovarian reserve'. A baby girl is born with all the eggs she will ever have for her entire life. In the ovaries, these eggs exist as follicles: a single egg surrounded by a supportive layer of smaller cells known as granulosa cells. These follicles make up the ovarian reserve, and it is this number that is used to project a woman's reproductive lifespan.

As a woman's eggs age, the frequency of genetic abnormalities increases. These abnormalities can cause genetic disorders (such as Down syndrome) and decrease the chances of a baby being carried to term.

There is nothing that can be done to increase the number of eggs a woman possesses, and some women are opting to have their eggs frozen at a younger age to increase their chances of a healthy pregnancy in later life.

However, this technology is far from perfect. Egg harvesting requires intensive hormone treatment and an invasive clinical procedure. Following that, the defrosting process is still fraught with risk and eggs can be lost when revival is attempted later down the track.

While lifestyle choices have no consequence on the number of eggs a woman possess, they can impact the health of these eggs and her overall reproductive health.

We know that obesity can cause hormonal imbalances which can disrupt ovulation cycles and increase the chances of problems developing during the pregnancy, such as gestational diabetes. By the same token, underweight women can also have trouble conceiving.

Unsurprisingly, smoking is known to be detrimental to reproductive health. However, research has also shown that a woman's mother's or even grandmothers' smoking status can impact her chances of conceiving a healthy child. When a mother smokes during pregnancy, the developing female embryo and its eggs are directly subjected to cigarette smoke and its toxic constituents. And although cigarette smoking rates are in decline, 14 percent of Australian women continue to smoke while pregnant.

Declining fertility rates have resulted in a steady increase in the use of assisted reproduction. In 2013, in Australia alone, over 70,000 IVF cycles were performed, costing the government approximately $240 million per year.

Assisted reproduction can aid couples affected by male-related infertility, as well as address some aspects of female infertility. However, it has yet to advance to a point where it can effectively rescue fertility in all cases, with a less than 20 percent success rate for current treatments.

Certainly, we are seeing some scientific advancements in several areas aimed at prolonging female fertility. But the unfortunate truth is that human biology is not evolving at the same rate as the society we live in.

We are subjecting our bodies to toxins detrimental to our health and fertility and ignoring the harsh realities of our aging ovaries.

From a scientist's perspective, the best idea going forward is that we need to accept that there are some aspects of our biology that we cannot change. Rather than waiting for research to extend female fertility, what we need is change in attitude and culture. This requires not just improving education on fertility, but a shift in politics and supportive infrastructure whereby having a career and having children does not need to be mutually exclusive.