Twin Pregnancy Update: Ultrasound Findings & Baby Growth (7 Weeks)

Question
I am 27 years old and pregnant for the 6th time.  I have two children, 8 years and 3 years and have suffered 3 early miscarriages.  My last period was May 13, 2004.  I had an ultrasound about 2 weeks ago which showed two gestational sacs, one a little smaller than that other.  Today, I had a follow up and found two babies, both with good heartbeats.  Twin "A" was 156 and Twin "B" was 162. Both measure about 7wks and a few days.  Twin "A"'s sac is considerably smaller than Twin "B"'s though and the doc said that this could result in a vanishing twin - however, with the good heartbeat and measurements, may progress normally.  What is the chance of a vanishing twin after a strong heartbeat and good measurements?  And what effects does a vanishing twin have on the surviving twin?  Thanks!

Answer
By 8 weeks gestation, it is doubtful that, if you saw twins already, there will be a loss of one twin. However, there have been many cases of "vanishing twins" . When you get your next sonogram (around 29 weeks) you will see if there are one or two babies. If there is only one remaining, then the other twin has resorbed, which can occur from time to time. There is not much you can do to prevent the vanishing twin syndrome even if there was a good FH in the first trimester. HOwever, there is certainly a good chance of survival for both twins. Good Luck.