Fraternal Twins Run in the Family, says Study

There’s always been something about twins…

The prospect of conceiving two at the same time can be terrifying for a few (okay, most) – as is the wonder at how they’ll both fit inside the already limited confines of a uterus.


On the converse, matching outfits, and gummy smiles, are totes adorable.

Perhaps the most predominant preoccupation with the idea of such a twosome is the uncertainty of whether the possibility of having them is in your future.

New research may make things a little clearer though, helping experts to determine whether some could have twins on the cards.

According to a recent study, possessing a distinctive pair of genes can increase the chances of becoming a mum to fraternal twins.

Fraternal twins are conceived when two separate eggs are fertilised by two separate sperms. The gene variant FSHB increases the odds of this occurring by 18 percent. The gene is linked to higher levels of the follicle-stimulating hormone (FSH), which makes it more likely that a women’s ovaries will work overtime; releasing more than one egg per cycle. When there’s multiple eggs, there’s of course more pickings for the competitive sperm to battle over.

Another genetic variant called SMAD is responsible for upping the potential for fraternal twins by 9 percent. Simple arithmetic concludes that childbearing women who possess both genetic variants have a 29 percent greater chance of being able to play matchy-matchy with baby outfits.

Researchers performed genetic analysis on over 5,500 women who had conceived fraternal twins, both with and without the aid of fertility treatments. They also studied the genetic information of more than 300,000 women who did not have twins.

The research is ongoing, and could represent a breakthrough in certain fertility issues; FSH is injected to stimulate the ovaries and eggs for IVF, but some women’s ovaries respond too strongly to this – hence the production of multiple eggs.

“There’s an enormous interest in twins, and in why some women have twins while others don’t,” study author Dorret Boomsma, Ph.D., said in a release for the study. “The question is very simple, and our research shows for the first time that we can identify genetic variants that contribute to this likelihood.”

The researchers plan to create a genetic test to identify women who are candidates for carrying twins.