This is the first ultrasound that we took at 5.5 weeks. We found out that we were having twins (see the two sacs). We were so excited that we started asking the doctor tons of twin questions, before he stopped us and said that we should wait until the next visit to see if they would both grow. Next visit came and to our disappointment, one of them had stopped growing and the other had taken over normal development. So, in an effort to understand this phenomenon, I did some research on Vanishing Twin Syndrome and this is what I found.
*It is estimated that up to 50% of all conceptions are twins, however the mother never knows because the second twin stops developing before it is seen on an ultrasound.
*Until ultrasound technology became routine, one would not know whether they were carrying twins or not very early on in the first trimester.
*Because the second twin stops growing so early in pregnancy, it poses no risk to the live embryo or the mother, the body just simply metabolizes the second twin and the surviving twin is born healthy.
*Most women usually have their first ultrasound at 8 to 10 weeks, so the body would have metabolized the second twin by then and nobody would be the wiser.
*Unfortunately, it is usually beneficial for the second embryo to stop growing, as doing so usually indicates severe problems (genetic, structural,metabolic) in the second embryo anyway.
*The emotional impact of this phenomenon is not so bad as a miscarriage or life threatening pregnancy difficulty. We were a bit bummed, but knowing the facts and commonality of this phenomenon just made us grateful for the baby we have:)
So, just an anatomical and physiological curiosity for everyone.