This entry is submitted via Creative Reporter:

With more and more women delaying motherhood until their thirties, forties, or even fifties, researchers may have discovered nature's way of beating the "baby gap".

It is well known that a woman's fertility declines with age, but there is also a greater chance that she will give birth to non-identical (fraternal) twins. The reason for this paradox was unclear, until the publication of a new study from
Vrije University.

When researchers measured levels of a hormone called FSH (follicle-stimulating hormone) in women undergoing fertility treatment, they found them to be highest in women aged over 35 and lowest in those in their twenties.

FSH is important because it triggers the maturation of egg-containing follicles in the ovary. In most monthly cycles, only one follicle releases an egg. Fraternal twins occur when two eggs are released and both are fertilized.

As women get older, the number and quality of their follicles decline. At the same time, FSH production increases, to ensure the release of an egg from one of the few remaining good-quality follicles. The Dutch researchers suggest that, if two good-quality follicles are present, rising FSH may be enough to cause the release of two eggs, increasing the chance of twins.

Given current concerns over falling birth rates, these results may be significant, particularly for older women who risk "having it too late".

by Wendy Anne Prosser, a freelance writer and editor.