The skin is like a large layer of spandex covering the body. If you pull on your skin and let go, it will snap back into place. When the skin is forced to stretch beyond the capacity of its natural elasticity, as is the case with rapid growth during pregnancy, stretch marks may form. The presence of increased cortisone levels in the body during pregnancy exacerbates the problem. Typically during pregnancy stretch marks occur over the abdomen, hips, buttocks and breasts.

Seen under a microscope, a stretch mark will reveal only a few elastic fibers in the centre and an abundance of curled and clustered elastic fibers at the edges. The collagen fibers, which are protein building blocks of the skin, are separated rather than grouped into bundles. These changes take place in the second layer of the skin, the dermis.

Initially stretch marks appear as red and purple lines of varying lengths and widths. Sometimes they are wrinkled and shiny. Gradually they fade to a color or shade lighter than the surrounding skin and remain that way.

So, for Kate the million dollar question is whether or not she can prevent stretch marks during pregnancy and the answer is no. There are an abundance of topical products on the market containing agents such as Vitamin E and aloe vera which claim to prevent stretch marks. These products will probably not work and they may actually result in allergic reactions.  There are also claims that moisturizing and massaging the stretched skin will encourage circulation and therefore keep the building blocks of the skin healthy. It is unlikely this will help to prevent stretch marks but it may help with the itch that sometimes occurs with dry, stretched skin.

A healthy diet rich in vitamins and minerals contributes to healthy skin and a healthy baby. Kate should also avoid unnecessary weight gain. Excess weight adds more stretch to the skin increasing the likelihood of stretch marks.

If stretch marks occur, what can be done? Some will resolve on their own once the skin is no longer under pressure and the hormones are back to normal. Others may have to be treated. Topical agents containing tretinoin in very high doses has proven effective in realigning some of the collagen and elastins in the skin. Unfortunately it is a very irritating course of action.

In the early stages of stretch mark formation when the striae are still reddish, purple in color, treatments with vascular removal lasers have proven to reduce the redness and realign the building blocks of the skin. This is the best treatment for improving the appearance of stretch marks.

Treatments to older stretch marks with lasers such as the DeepFX carbon dioxide laser have proven helpful although far from magical.