If you're a firstborn, we have some bad news for you...

If you're a firstborn, you may have always felt like your little sister/brother is more genetically blessed than you...

Well, now it has been 'confirmed'.

A new study, which looked at more than 26,000 Swedish women, has revealed that firstborns were nearly 30 percent more likely to be overweight than their younger siblings was.

It's not to do with genetics though, it's purely because of birth order.

As reported by Today.com, researchers suspect that conditions in a woman's uterus change after her first baby is born which reprograms metabolism and the regulation of fat for the next newborn.