Vanishing Twin Syndrome occurs when one or more fetuses disappear from the womb during pregnancy, usually resulting in a normal singleton pregnancy.
There is a great deal of speculation about the psychological and emotional impact of VTS. Due to a deep longing for some undefined, missing part of themselves single twins (survivors) may experience problems with relationships and/or even with sexual identity. They often suffer from unreasonable feeling of responsibility or guilt. "If I had only done more.....if only I did it differently...." Troubling, recurring dreams of their twin(s), fear of sleeping alone, sudden feelings of loss or abandonment, profound loneliness, eating disorders, extreme emotional sensitivity, and even schizophrenia, etc, may befall survivors of VTS. Many are left-handed.
If people are not aware they are twin survivors, they have no context in which to place these very confusing emotions. If the survivor is aware of what happened, the trauma can be processed and overcome, sometimes quite rapidly.