How many weeks pregnant before you know if its twins or not?

Answer 1

they should be able to tell right away but sometimes the twin is hidden behind the other one.They can tell right then and there if they give you an internal ultrasound but sometimes the regular ultrasound dont get all the way around the uterus so the twin could be hidden.

Answer 2

Typically, twins are discovered on an early ultrasound, somewhere between 7-9 weeks gestation. In regions where ultrasounds are not performed that early in pregnancy, your doctor may be able to find two heartbeats using a doppler a little later than this. Also, if your uterus feels large upon examination or your morning sickness is especially severe, your doctor may suspect a twin pregnancy.