HOW TO PREVENT CANCERS

by Dyani Lewis

Headlines often highlight the perils of getting pregnant over 35. But how much does being an older mum affect a woman's health or her baby's?

In recent decades, Australian women having their first child have been older. The average age for a first child has crept past the age of 30, and women aged 35 to 39 years have been outbreeding their 20 to 24-year-old sisters since 2005.

Fertility concerns aside, even women who naturally fall pregnant in their late 30s or 40s are often plagued with fears over the possible health risks their age poses for themselves and their babies. According to Associate Professor Mary Carolan from Victoria University, these fears are often overstated. "[Older women] get a lot of bad press," she says.

Carolan worked for many years as a midwife before embarking on an academic research career. She says older women's anxieties during pregnancy are often provoked by a barrage of information from healthcare professionals about potential risk factors associated with a mother's age. "I think it's very disheartening for them," she says.

Carolan has looked into what the risks are for women aged 35 years or older – women who are officially classified as being of advanced maternal age – who choose to have a baby.

"I felt that there needed to be some positive information out there for these women," she says.

"As we age – all of us – are more prone to certain things," says Carolan. "It's true, there is a connection between older maternal age and all sorts of adverse outcomes," she concedes, but notes that the data needs to be considered in the right context.

One of the most known risks associated with older motherhood is conceiving a baby with Down syndrome, in which a baby receives one too many chromosomes from their parents. Instead of having a total of 46 chromosomes, they have 47; an extra copy of chromosome 21 results in the child having a distinct appearance and intellectual disability.

Either parent can contribute the extra copy of chromosome 21, but in 90 per cent of cases it comes from the mother and is due to faulty cell division during egg development. The older a woman is, the more likely this is to occur.

The chance of having a baby with Down syndrome at age 30 is around 1 in 1000. By the age of 35, the risk has increased to 1 in 400, and by 40, to 1 in 100.

While the increase in risk might seem alarming, Carolan points out "your risk of having it is still very much smaller than your likelihood of having a normal baby".

Most foetuses with chromosomal anomalies resulting from faulty egg maturation often don't make it past the first few weeks of pregnancy. If this occurs early enough, a woman may not even know that she has been pregnant.

Screening towards the end of the first trimester – at 11 to 13 weeks gestation – is a further check for Down syndrome and other health problems that the foetus might have.

Other chromosomal conditions caused by incorrect cell division in the maturing egg include:

Klinefelter syndrome – an extra copy of the X chromosome in boysPatau Syndrome – an extra copy (trisomy) of chromosome 13Edward Syndrome – an extra copy (trisomy) of chromosome 18

As women age, the hormonal ebbs and flows that occur with clockwork regularity at 20 start to falter.

"The wheels start to come off a bit," explains Dr Mark Green, a reproductive biologist at the University of Melbourne.

One of the results is that the rate of multiple births increases. Women aged 35 or over are twice as likely to have a multiple birth as those under the age of 35.

Hormonal fluctuations are also often behind the "whoops" babies, as Green calls them. These are babies conceived when women make the mistake of thinking they've entered menopause, but instead their cycle has simply become more irregular as menopause approaches.

Older women pregnant with just one baby have slightly higher risk for certain conditions than younger women. These conditions include gestational diabetes, high blood pressure and stillbirth. But this risk is still low.

"As a woman gets older, the very small risk [of stillbirth] increases," says Carolan. But, she notes, the absolute risk is very small. "In places like Australia, it's so low that you can't really get reliable statistics on it."

In good news, a study conducted in Western Australia also shows that stillbirth in older women is decreasing.

While women aged 35 and over are twice as likely to get gestational diabetes, which can affect the baby's health, ethnicity and a mother's weight also influence a woman's risk of developing gestational diabetes.

"Women that are obese or significantly overweight are way more at risk than a woman who is lean and active," says Carolan. Also certain ethnicities are more at risk, including women from Vietnam, South Asia, Africa and the Mediterranean.

As obstetric and midwifery care have improved and complications, such as high blood pressure, are identified and treated early, outcomes for older women and their babies have also improved.

Another positive change is that many older women having babies now are fit and healthy when they go into pregnancy, which often has a greater impact on the pregnancy than age.

"What we can definitively say is that a woman that goes into a pregnancy over the age of 35, who doesn't have any of these pre-existing conditions, like diabetes, high blood pressure, and is within a normal weight range and eats well, you can say that her outcomes are likely to be really good," says Carolan.

A few years down the track, their children may even be doing better than those of younger women. Having waited for financial security, or to establish a career, older mothers can be better equipped to give their children the best start in life.

"Socially, the children of slightly older mothers do well," says Carolan. "They do better than many of the children of younger mothers."

Published 31/10/2013