Anyone have twins after singleton ultrasounds?

It is very rare for a singleton pregnancy to turn out to be a twin pregnancy. Most often this is not recognized until at least one fetus is 12 weeks in gestational age. There are some cases where a singleton pregnancy could turn out to be a twin pregnancy because one fetus is hiding behind the other or when the fetuses have a fused placenta and appear as one. In a singleton pregnancy, there would only be one fetal heartbeat detected instead of two. Once the second heartbeat is detected, it cannot be a fetus that simply was not seen before during ultrasounds.