Verified answer

That would happen when you have fraternal twins (2 eggs fertilized at the same time) and one egg makes it to the uterus, and one egg does not, and it stays in the fallopian tube.

This happened to me.

I was a few weeks pregnant and went in for an u/s because I am epileptic I have to have one 1x/month. They found that I had an ectopic pregnancy and I started to miscarry a few days later (I was lucky I didn't need surgery). About 6 weeks later I still wasn't feeling well and went to the dr and it turned out I was still pregnant! Turns out I was pregnant with twins (I had ovulated twice that month apparently) and one egg never made it all the way down. The healthy pregnancy was just hidden that first time around. So yes, it can happen. Rarely, but it can and does happen.

Twins in separate sacs (fraternal twins) one sac travels to the uterus and attaches itself properly and the other sac travels to the tubes and causes an ectopic pregnancy... They just had something like that on TV over the weekend on one of those cable channels--I watched it ... the one twin actually SURVIVED living outside the womb---and both twins were delivered early and put in incubators... but they DID live.... I was amazed because I didn't think a baby COULD have survived outside the womb----I guess it all depends on where the plecenta attaches..... IF the plecenta had attached itself to any other organs, it would have basically EATEN that organ (according to what they said on this tv program)...."the plecenta feeds off of whatever organ it attaches itself to"....don't ask HOW it survived, I don't know---