1999-06-17-18 Synechial band (or amniotic fold) as a differential diagnosis for vanishing twin© Tomko www.thefetus.net/

buddy@redrose.net

History

A 35-year old G₂P_0,0,1,0 presented for a first trimester ultrasound to establish dates to schedule a Chorionic Villus Sampling for advanced maternal age and gender determination due to history of hemophilia carrier. The patient had undergone a dilatation, curettage and evacuation 14 years before this pregnancy. The appearance of a twin gestation was noted on the initial 6.5 week scan. One sac did not contain an embryo. The other sac had a fetus with regular fetal heart motion. The patient had a repeat b-hCG at 8 weeks which showed levels >100,000 units (universal standard).

A subsequent scan was done showing a smaller misshapen sac and a live pregnancy in the other (growing) sac.

A repeat b-hCG at 10 weeks showed decrease in b-hCG values. It was supposed at that time that this was most likely a vanishing twin phenomenon. A repeat scan at 3 days later, for a second opinion, showed a thin band-like structure thought to be encroaching the fetal head.

It was realized at this point that this was a thinning synechial band (or amniotic fold) which was not endangering the fetus. With current 2-D imaging technique and lack of follow-up it is easy to see how the diagnosis of vanishing twin was made.

To avoid repeating this confusion, it may be prudent to ask the patient if she has a history of surgical instrumentation to the uterus (which may result in synechial bands).