The chances of having twins also goes up with older age and certain pregnancy methods such as in vitro. (businessinsider.com)
Of course, this doesn't mean that gaining weight will increase your odds of having twins. (verywellfamily.com)
While it is not entirely definitive and accurate, a blood test can be a great way to assess a woman's likelihood of having twins in her womb versus just one child. (checkpregnancy.com)