What age is best for having children?

Mother and Baby
Monday, July 14, 2008
Best age to have kids. Image: Getty

Is there an ideal age to have kids? If so, what is it?

Some people say the best age to have a baby is when you are physically, mentally and financially ready, but is there a time when you're all of these things at once?

You may be at your physical peak in your twenties, but mentally you may be 10 or more years away from starting a family. Financially, you may not be secure until you reach retirement age! So is it possible for there to be an ideal age to have a baby?

The way we were
Since you were born there's been a major shift in the age that women are having their babies. In 1971, the median age of mothers giving birth was 25 years, according to the Australian Bureau of Statistics. By 2001, the median age had jumped five years to 30. During this time, women aged 30-34 years had the highest fertility of all age groups, while the fertility of women aged 20-24 years continued to decline. In 1982, women in this younger group accounted for 104 babies per 1000 women, but by 2002 it had almost halved to only 56 babies per 1000 women.

It's believed these changes in childbearing age reflect women's greater control over their fertility and a tendency for women to delay having babies due to more education and employment opportunities. And it's not just women making these decisions, says Dr Dianne Rudd, senior lecturer at Adelaide University.

"Boys aren't necessarily flocking to do it early either and parents don't expect their child to leave home and get married at a young age," Dr Rudd says.

Another contributing factor is the assumption that you can delay having a baby because if you run into fertility problems later you can fall back on IVF, says Dr Kelton Tremellen, deputy medical director at IVF clinic Repromed.

"Some very prominent women, such as Hollywood stars, have had babies at the age of 47 with the aid of IVF. The reality is they're using donor eggs from younger women and are having those eggs impregnated by IVF. It creates a false expectation that people think they can fall back on IVF," he says.

Biological clocks
For women, fertility remains fairly static until the age of 30, then it starts to decrease.

"By the time a woman reaches 35, it takes her twice as long to conceive as a women who is 30 or younger and by the time she reaches 40, it takes her four times as long as a woman who is 30 or younger," says Dr Tremellen. "It's a rapid drop off. The average couple under 30 will conceive in around three to four months. When you get to 40, it's more like nine or more months."

You probably know women who've had successful pregnancies and healthy babies in their forties. While it is possible, it's worth knowing that these women are at a higher risk of complications than younger women. They're more likely to get diabetes and have high blood pressure, which can result in conditions such as pre-eclampsia, premature delivery, placental problems and even some birth defects.

The risk of having a baby with chromosomal abnormalities, such as Down's syndrome, is significantly higher in older women compared to younger women, too.

The miscarriage rate increases with age as well. While the figures seem to vary, some reports say it goes from about one in seven for women younger than 25 to as high as one in two for women in their mid-forties. Additionally, if older women do have fertility problems, there's less time to seek effective treatment.

"In our experience in IVF, trying to conceive beyond the age of 44 is almost impossible. Women don't have as many eggs left but the egg quality is also a problem," says Dr Tremellen.

"A common misconception is that if you don't fall pregnant before age 44, you just turn up for IVF and they give you drugs and that will fix the problem," he says.

"However, the quality of the eggs we get out is predetermined by the woman's age, and drugs can't change that. Eggs we get from a 44-year-old are 44-year-old eggs. They don't work that well and the genetic abnormality rate is high and miscarriage is high."

Most worryingly, he says 10 percent of women have premature ageing of their ovaries, so they're critically running out of eggs by 35.

What about men?
While the outlook isn't great for women who let their biological clocks tick too long, Dr Tremellen warns that men also shouldn't think they can delay having a baby without seeing consequences.

"It's not as dramatic for men as for women — there are blokes in their nineties who can conceive. But studies show a slow decline in sperm count and swimming activity with time," he says.

"What's really worrying is that as a man gets older, the amount of DNA damage in his sperm increases. There's now been a link between that DNA damage and illness in children. For example, dwarfism (or achondroplasia) is more common if the father is older. That's because the gene in that condition gets mutated as you get older," Dr Tremellen says.

"Other studies have found that the older the father is, the higher the chance of his child having schizophrenia. So it's not entirely true that men are ready to roar right up until they die."

The ideal age for men to start having babies is before 30. Studies have shown that the older the man gets, the longer it takes to conceive, even if his partner is young.

"A US study found that as a man gets older, the free radical damage in his sperm increases and in turn causes DNA damage, which can cause infertility," Dr Tremellen says.

Mums of the future
So with so many of us delaying parenthood, it would seem fertility problems are going to be more common in the future. It's a problem the Fertility Society of Australia is trying to tackle. In 2006, they performed two national surveys that revealed alarming misconceptions about fertility in both the community and among healthcare providers. As a result, they believe there's an urgent need to provide clear, consistent messages about fertility and how to preserve it, both to healthcare professionals and Australian men and women on a national level.

While it makes sense for health professionals to be encouraging women to have their babies at a younger age, the message isn't always received well.

"I've said things like this in the past but have been howled down as a caveman who's trying to keep women barefoot and pregnant in the kitchen," says Dr Tremellen. "I tell them they'll always have the opportunity to advance their careers but they won't always have the opportunity to have children."

However, the fact is that it isn't always possible for a woman to have a baby before she's 30. She may be just starting a career, paying off huge university debts or hasn't met the right man yet.

In this case, Dr Tremellen believes there is a need for technological advances where women can freeze eggs or at least have a liberalisation around the laws concerning donor eggs.

"At the moment you can't pay egg donors, but in the US you can and they have no shortage of egg donors. I understand there are ethical issues and problems with coercion and people regretting it later on in life, but it certainly deserves consideration," he says.

With these advances in technology, it would become increasingly possible for much older women to give birth, even beyond menopause (which is usually around 51).

"The uterus doesn't really age," says Dr Tremellen. "Fibroids are more common with age and if they're large, can affect the attachment of the embryo. But in general there's nothing wrong with the uterus even past menopause if you're given the right hormones."

So will we see women aged 70 becoming mothers in the future? Dr Tremellen says it's unlikely. "You have to ask, is it in the best interests of the child? Here in Australia you wouldn't treat women beyond the age of menopause. In fact, legally you are not allowed to because it's not in the best interest of the child," he explains.

"If you put eggs into a 60 or 70-year-old woman, who's looking after that child when the mother dies in 10 years?"

All material is © Mother & Baby: Making Babies

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