The reason Meghan Markle's quick pregnancy is giving women the wrong idea.

Well, that was quick.

Prince Harry and Meghan Markle’s baby is due in the UK spring. Considering that the couple only got married in May, it seems likely that they fell pregnant after just a month or two of trying. (Without wanting to sound grossly intrusive.)

And yet we’re always being told that women’s fertility declines after the age of 30, and we’re taking a risk by waiting till our late thirties to start a family.

So what’s the truth?

President of the Fertility Society of Australia, Professor Michael Chapman, says 37 isn’t “old old”. The chance of a woman that age falling pregnant is somewhere between 12 and 15 per cent per cycle.

“I talk to patients about the roll of the dice,” he tells Mamamia. “One in six is 15 per cent. You can roll a dice and get a six first time.”

That could be exactly what Meghan and Harry did. Lucky them.

But Professor Chapman is concerned that Meghan falling pregnant so quickly could send the wrong message to thirty-something women.

“Unfortunately, Meghan getting pregnant at 37 potentially makes people think, ‘Oh well, it will all be all right. I’m only 35. I’ll wait till I’m 37, because Meghan got there.’ It is potentially a negative.”

Chapman says fertility rates do drop between 35 and 37.

“There’s probably about a 10 per cent decline. By 40, it’s gone down 50 per cent.”

Meanwhile, fertility expert Dr Karin Hammarberg, who is working on the Your Fertility campaign, says she was “so pleased” when she heard Meghan and Harry’s pregnancy announcement.

“I thought, ‘If they think they’re going to wait a few years before they even try to have a baby, it’s going to be disappointing,’” she tells Mamamia. “So they must have got the message and got onto it straightaway.

“Certainly, at 37, most women who try will, at least within a year, get pregnant. Meghan was fabulously fertile, obviously, and managed to get pregnant pretty much straightway. Good for her.”

Dr Hammarberg agrees that Meghan was lucky, but she thinks there might have been more to it than that.

“The thing about Meghan Markle is she’s a very healthy young woman. She probably exercises a lot. She is in the healthy weight range. She doesn’t smoke. She probably doesn’t drink an awful lot. All those things will increase a woman’s chance of conceiving. Lifestyle plays quite a big role here. The health of the woman and the man both actually make a difference to the chance of having a baby.

“In the case of Meghan and Harry, they’re pretty healthy-looking specimens, so I think that that probably would have helped them.”

She thinks Meghan should get through her pregnancy without any problems.

“I don’t think they would have announced it if she hadn’t had all the tests known to man. Pregnancy complications can happen to anyone, but with her health and her age – she’s still young, she’s 37 – it should all go well.”

After spending many years working in IVF, Dr Hammarberg has seen a lot of disappointment among people who are unable to have children. She’s a big believer in couples getting onto the business of babies sooner rather than later, if they’re of a similar age to Meghan and Harry.

“People find their life partner probably later in life these days,” she explains. “I think once you do find someone, the luxury of waiting for a few years to just enjoy life together is perhaps a little bit risky.

“I think it’s a conversation that people should have early in the relationship. If they both have the same wish, I think it’s good to proceed sooner rather than later. There’s not much IVF can do to improve the chance of having a baby when it’s age-related infertility.”

Dr Hammarberg also thinks that Meghan and Harry shouldn’t wait too long to have a second child, if they want to have another one after this one.

“If she wants to wait couple of years, she’d be 40,” she points out. “Forty’s quite a big cut-off, I think. But she’s probably more fertile than the average person.

“Anyway, it’s pleasing to see and she looks so gorgeous.”