Ischiopagi of monozygotic twins. However, studies have shown that these disturbances must happen at critical times in the pregnancy for the conjoined twins to develop. Conjoined twins are at high risk to being stillborn or dying shortly after birth. In some cases, a healthy twin and a parasitic twin are born. The parasitic twin has no hope for survival and dies and is then surgically separated from its twin. Depending upon how the twins are attached and what is shared among them, complications can arise from surgically separating the live twin from the dead twin. In Ischiopagus cases, the children share
There are known knowns management and strategic planning circles. Known unknowns refers to "risks you are aware of, such as cancelled flights..." Unknown unknowns are risks that come from situations that are so unexpected that they would not be considered. "For example, prior to the invention of the personal computer, manufacturers of typewriters probably didn't foresee the risks to their business". Contemporary usage is largely consistent with the earliest known usages. For example, the term was used in evidence given to the British Columbia Royal Commission of Inquiry into Uranium Mining in 1979: The term also appeared in a 1982 "New Yorker" article on