Tick, tock, tick, tock -- for women dreaming of becoming a mum, it's the most terrifying sound in the world.
But could it be your desire to look good in a super skimpy bikini, not that biological clock, which determines whether or not you can have a baby?
Reality TV star Chantelle Houghton this week revealed that years of crash dieting have left her infertile at just 27.
"Because of my obsession with food and my crash- dieting when I had bulimia, I've ruined my chances of having a baby naturally," she confessed to Heat magazine.
"[The doctor] told me that I'd never be able to conceive naturally . . . that I had low fertility and that if I wanted a baby, I'd have to have IVF.
"He said that if I'd waited another three years, I would never be able to have children. I wouldn't have any eggs left."
Chantelle is best known for winning Celebrity Big Brother in 2006 -- even though she was a 'non-celebrity' at the time.
But her newfound fame, coupled with a decade-old battle with bulimia, drove her to extreme measures for the veneer of perfection.
In the wake of her split from fellow BB housemate, pop star Samuel Preston, in 2007, the 5' 7" star's weight plummeted to eight stone.
Yet it wasn't until she went to a fertility expert complaining of stomach pain that the true devastation wreaked on her body by eating disorders was discovered.
"I've punished my body and now it's punishing me," says Chantelle of the diagnosis that she may never be a mother.
"I have tried every diet there is," she admitted in the past, "from body wraps and the Special K diet to just drinking water. I was obsessed from the minute I woke up in the morning until the minute I went to bed. Ultimately it's my fault. I hate myself and can never forgive myself."
Body fat is key to a woman's ability to get pregnant and stay pregnant. And shrinking below or ballooning above your recommended weight can throw reproductive hormones out of kilter.
In men, being dramatically under or overweight can slash sperm count.
"Crash dieting puts the body under huge stress, so of course that's going to take its toll," says nutritionist Dr Marian Faughnan of Safefood.
"Body weight has a huge impact on fertility -- women who are extremely underweight or overweight can stop menstruating and ovulating altogether.
"More commonly in Ireland, we see women who are on the overweight side experiencing fertility issues.
"But while it affects a smaller number -- and is therefore sometimes ignored a little, being underweight is just as big a problem for women trying to get pregnant."
Around 200,000 people in Ireland are affected by eating disorders, according to the Department of Health -- with anorexia estimated to affect one-in-150 15-year-old girls.
"When someone develops an eating disorder in adolescence, it can pretty much halt puberty," explains Suzanne Horgan, director of the Eating Disorder Resource Centre of Ireland."But that's an incredibly difficult message to convey to teenage girls.
"When you tell clients of that age that they could be damaging their fertility, they don't care -- some of them are quite happy to be infertile because they want to remain childlike.
"It's not until later on when they're trying to start a family that they realise the implications."
"Whether you're planning a pregnancy or not, every woman who's of child-bearing age and sexually active should be eating a healthy, balanced diet and taking folic-acid supplements -- just in case," says Dr Marian Faughnan.
Having beaten bulimia before becoming overweight and slimming down to a size 10, American reality TV star Khloe Kardashian admitted recently that she's now struggling to get pregnant.
"I thought I'd be pregnant by now," revealed Khloe (27), who's married to basketball player Lamar Odom.
"We've been working at it all year. I don't know what the problem is. If it happens, it happens."
However, it's not just anorexics and bulimics who could be playing Russian roulette with their reproductive systems -- even a last-ditch bikini diet can result in irregular periods impacting on fertility.
And as the 'Size Zero' generation matures towards motherhood, prepare to see more headlines about infertile twenty-something women.
"It's the next generation of girls who will really highlight this problem," predicts senior clinical embryologist Declan Keane of ReproMed Fertility Clinic in Sandyford.
"Today's cultural ideal of being super-skinny is likely to cause a continuation of fertility problems for years to come.
"Girls who want to eventually become mothers shouldn't rely on the 'magic wand' of IVF or egg-freezing.
"The ovaries are a limited resource," he warns. "So girls need to take steps to protect that now by eating healthily and taking folic acid, cutting out smoking and reducing their alcohol intake, getting enough exercise, developing a regular sleep pattern and protecting themselves against STIs.
"For someone like Chantelle, she needs to address her issues with food before even contemplating pregnancy."
In the meantime, the Essex star can take heart from the story of eating disorder survivor Katie Rhead (23) who defied medics to give birth to a tiny 3lb baby girl earlier this year.
Going public with her regret, Chantelle hopes to make other girls wise up to the potential cost of squeezing into their skinny jeans.
"All the time I was making myself sick, I was thinking 'Yes, I'm getting skinnier," she recalls. "I thought I was winning, but I was losing. It's cost me the chance of a family.
"Being stick-thin -- is it worth that?"
Source: Irish Independent