New study finds that you’re more at risk of vomiting and experiencing nausea with twins if you’re carrying at least one girl.

At a twin ultrasound 12 weeks scan you’ll often learn your twins chorionicity as well as your exact due date. This dating and chorionicity scan most often occurs when you’re between 11 weeks and 13+6 weeks pregnant.

Your twins chorionicity determines whether or not you can detect them on ultrasound at or around 5 weeks of pregnancy.

Researchers compare twins with abnormal Dopplers who’ve had laser surgery for Twin to Twin Transfusion Syndrome (TTTS). They look at changes and survival rate one week after surgery.

Read about how a twin ultrasound is done, what your sonographer should be looking for, and how often you should have scans.