Girls With Twin Brothers Pay A Price For Sharing A Womb With A Boy

Twins are supposed to have a special bond that allows them to connect with each other. They also usually get a lot of questions all through their lives about what it was like to be one of two growing up and how alike or different they are from each other.

A recent study, published in PNAS, found that being a twin isn't always the best thing, especially being a girl with a fraternal twin brother. The study apparently shows that a female who shared a womb with a male twin has fewer advantages growing up.

The researchers looked at data for over 13,000 twins born between 1967 and 1978 in Norway. Their findings indicate the female can have issues with future income, education, marriage rates, and even fertility.

Here are the numbers they are talking about. Females exposed in utero to a male co-twin:

  • Are 15.2% less likely to graduate high school
  • Are 3.9% less likely to complete college
  • Are 11.7% less likely to be married
  • Are 5.8% less fertile
  • Have 8.6% lower earnings over their life

It was a first of its kind study looking at people for more than 30 years, from childhood to adulthood. Researchers from the Norwegian School of Economics joined scientists from Northwestern University to examine the data.

The research looked at women who had twin sisters as well as those who had twin brothers. The ones with a male co-twin didn't fare as well as those with female co-twins. And this held true even if the male twin died before birth or shortly thereafter. 

Scientists came up with two possibilities for this issue: being exposed to testosterone in the womb and competing for nutrients. Source

Of course, the researchers pointed out that other factors play a role in the outcome. And a female with a male twin won't necessarily have these issues. Also, the findings come from people raised in Norwegian society, so the results may not reflect other cultures or societal settings.

For women out there with a male co-twin, you are the one who has the ability to decide how your life turns out. Not your brother. Not your parents. You.

So, are you part of a male/female set of twins? Do these findings ring true for your family? Let us know below. Even if you aren't a twin, please tell us your thoughts and pass the link along to others.