Clearly, she was trying to look cutting-edge and youthful. But when 53-year-old Madonna bared one of her breasts on stage earlier this month, it also revealed a distressing reality for many women – saggy bosoms that have lost volume and pertness with age.

So what causes breasts to sag?

And can anything be done to keep our most feminine assets in their prime? Experts have their say.

Fighting gravity’s in your genes

No other part of the body is more affected by the force of gravity than the breasts.

From the moment a woman’s chest is fully grown, in her late teens to mid-twenties, she faces an uphill battle to defy the downward pull.

The challenge is down to the fact that there’s not much of a natural support structure to keep them in place.

Breast specialist and surgeon, Ian Laidlaw, of Frimley Park Hospital, Surrey, UK, says drooping breasts can have a serious psychological impact on a woman.

He says: “A large part of a woman’s femininity is her breasts. Sagging is a predictable change, yet it can have a profound impact.

“The feelings women get when they can’t control the changes in their breasts can include inferiority, distorted body image, unattractiveness and worthlessness.”

The condition even has its own medical name – ptosis – and droopiness can be graded by doctors on a three-stage scale.

In pert, young breasts, the nipple is usually above the line where the base of the breast meets the chest – or the inframammary fold.

By stage two, the nipple is around 2.5cm to 7cm below that point. At stage three, the breast hangs more than 3cm below, with the nipple often pointing down to the floor.

Over a lifetime, a woman with heavy breasts may see her nipples drop by as much as 10cm or 11cm if they descend to her waistline.

Breasts are made of a mixture of mammary glands and fat.

Through this run hundreds of pieces of tissue which connect the bulk of the breast to the skin – and keep the breast suspended.

How pert your breasts stay depends partly on the genes which govern how much fat, glands and connective tissue they contain.

Generally, the more connective tissue and glands you have, the firmer and more buoyant your breasts are likely to be.

Size will also dictate how firm they stay. The heavier they are, the more strain on the skin, and supporting ligaments will stretch permanently under persistent pressure.

Try to keep your weight stable

There are two places where fat is found in the breast. Seventy percent of breast fat is mixed with the glands to form the main bulk of the bosom.

The rest of the fat is found in a layer of padding just under the skin. It’s this that tends to fluctuate in thickness as you gain and lose weight.

If this layer thickens dramatically – and then thins out again because of yo-yo dieting – it will permanently stretch the supporting skin, leading to a droopier chest. As women become more buxom, they are more likely to face sagging.

That’s because the rise is mainly because of an increase in fat content in the breasts – and fat is heavier and therefore harder to support.

Laidlaw says: “One of the best things you can do for your breasts is to maintain a constant body weight for your height that’s within the recommended range.”

Don’t worry about breast-feeding

Women have long blamed their saggy booby on breast-feeding.

Yet research has found that it’s the expansion and contraction of the milk glands triggered by pregnancy, rather than breast-feeding, that causes droopiness.

In one American study, an academic interviewed 132 women seeking breast lifts or enlargements. Just more than half had breast-fed at least one child for an average of nine months.

Researchers found no difference in the degree of sagging between women who had breast-fed and those who had not.

Laidlaw says: “Women should definitely consider breast-feeding – especially as the health benefits for the baby far outweigh any possible effects on the breasts.”

Stub out those cigarettes

Like anywhere else on the body, the skin on the breast includes a network of collagen fibres, which make it firm, and elastin to make it flexible. Over time, these fibres break down.

The rate at which skin cells renew themselves also slows as we get older.

Just as on the face, it’s important never to expose the breasts to too much sun because ultraviolet exposure will break down collagen and elastin.

And in the same way that smoking leads to wrinkles, it also leads to the deterioration of breast skin.

Laidlaw said: “The effect on a woman’s breasts is so marked that it is possible to see if she smokes just by looking at the condition of her breasts. Even giving up smoking after a number of years will lead to a marked improvement.”

He says he is sceptical about skin creams containing oestrogen and vitamin E, which promise to improve breast pertness.

“You can absorb oestrogen through the skin, but it’s not a very efficient way of doing it, compared to HRT,” he says. “If these creams really worked, doctors would be recommending them.”

Exercise – but beware the bounce

There’s both good and bad news when it comes to exercise.

The right regimen can keep your breasts pert by improving blood supply.

While there is no muscle in the breast itself, it is possible to build up the underlying pectorals for a lifting effect.

But some activities – particularly running – can take their toll.

When you run without proper support, the breasts bounce in a figure of eight, causing wear and tear on the supporting ligaments.

Jenny White, of the Research Group in Breast Health at the University of Portsmouth, says: “We have found that breasts move an average of 10cms – up and down, side-to-side, and forwards and backwards.”

The larger your cup size, the greater the force on the breasts and the more they need to be restrained to avoid damage to connective tissue and ligaments.

Yet researchers estimate that, of the 12 million British women who regularly exercise, three-quarters do not wear a proper sports bra – even though they can reduce bounce by up to 74 percent.

You can’t help your hormones

Oestrogen is the main hormone influencing how your breasts look.

It’s this, the female sex hormone, which first makes the breasts grow – and stimulates the development of a tree-like network of milk ducts leading to the nipple.

Every month, as part of the menstrual cycle, rising levels of oestrogen prepare a woman’s body for possible pregnancy.

One side effect is that it stimulates the breast tissue by making it expand and retain water.

After menopause, when oestrogen levels begin to fall permanently, milk ducts and glands “go into retirement” and shrink – making the breasts feel emptier.

The tissue which makes breasts firm also shrivels and gets replaced by fat, which is heavier and less able to withstand gravity. – Daily Mail

Delay the droop

l Eating a healthy diet, including plenty of Vitamin C, may support the collagen and elastin in the skin.

l Maintain a moderate, ideal weight to avoid permanently stretching the supporting skin.

l Change your sports bra. Bras with separate moulded cups reduce bounce better than bras which simply strap the breasts closer to the chest.

l Avoid topless sunbathing and use sun screen on your chest and cleavage. Exposure to UV rays damages your skin’s ability to support your breasts.

l Push-ups and chest presses can build up the pectoral muscles and lift the level of your chest.

l Although there are risks, some women facing the menopause can maintain the levels of breast-boosting oestrogen with hormone replacement therapy.

Some versions of the combined pill will also keep oestrogen levels higher for longer.