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Vanishing Twin Syndrome

A Mysterious Occurrence in Multiple Pregnancies

By Teri Brown

There's an odd occurrence in obstetrics that still has doctors scratching their heads: vanishing twin syndrome. Its exact cause is still unknown to the medical profession, though there are some good theories on why it occurs.

Some women are diagnosed with twins early in their pregnancy only to find that one of the babies has vanished in a subsequent ultrasound. Others are diagnosed with twins, then miscarry one of the fetuses at a very early stage while the other baby goes on to have a perfectly normal delivery. Or, as in Pamela Kock's case, they don't find evidence that another baby was there until the birth of their healthy singleton.

Kock, a mother of two from Cincinnati, Ohio, had an easy and uneventful pregnancy until her 37th week when she developed symptoms of pre-eclampsia. She was ordered to begin maternity leave and stay in bed. One week later her doctor told her the placenta was no longer working efficiently and labor should be induced.

"After my daughter was born, my doctor pointed out that the placenta was double-lobed, which indicated that there had been, at some point, a twin," says Kock. "She called this phenomenon 'ghost twin' and said it was likely the reason for my complications. This twin must have disappeared very early because there was no indication of a second fetus when I had my first ultrasound at 11 weeks of pregnancy."

Michele Decoteau from Millbury, Mass., had a different experience. She knew about the twin ahead of time, but the outcome was the same. During an ultrasound exam in her 6th week of pregnancy, another embryo was noted, but it looked younger and somehow not "right" to the technician.

"My hormone levels were very, very high at that point so twins were not out of the question," says Decoteau. "We went in every week for three weeks and the second egg sac disappeared at about 10 weeks. When my son was born, there was a second small placenta. I was told by the nurse that he had a ghost twin – not uncommon, but most moms never know."

Want to see more?

• Two Babies, One Sac, More Risks: The Triumphs of Monoamniotic Twins
• Keep Those Babies in There: Avoiding Premature Delivery With Twins
• The Home Stretch: Surviving the Last Trimester With Twins
• Talk about it!