when do you find out your having twins
Your sonographer will use this information to try to work out if your twins are identical. Your first scan is likely to be your dating scan, between 10 weeks and 13 weeks plus six days (NCCWCH 2011, NICE 2011). This may also be the first time you find out you're expecting twins at all, so there'll be a lot to take in.
You should be able to find out whether you're having identical twins during a first trimester ultrasound scan. Before 14 weeks, it's easier to see on a scan whether your babies each have their own placentas and membranes (NCCWCH 2011, NICE 2011, RCOG 2008).