How early can a doctor detect a twin pregnancy? What would be the best method to detect it?

--Tanyita

Without a doubt, an ultrasound is the best way to detect twins. Without this exam, it may be difficult to discover a woman is carrying more than one baby. Sometimes two distinct heartbeats will be heard. Or the uterus may be larger than it should be, especially after 16 weeks or so. Still, in the past, many twin pregnancies were not detected until delivery!

Today, with routine ultrasound exams, most twin pregnancies are diagnosed by 20 weeks, many earlier. An ultrasound done at five to six weeks will show two sacs or two (or more!) embryos. It is uncommon to miss identifying a twin pregnancy on ultrasound.