Huffington Post by Robin Wilkey Posted: 12/14/2012 8:59 pm EST | Updated: 12/14/2012 8:59 pm EST

A Bay Area family got a holiday miracle last month thanks to help from Lucile Packard Children's Hospital at Stanford.
On November 7, Allison and Kevin Carlson celebrated the birth of their twin baby girls, Kate and Annie. But the girls weren't just any twins: they were monoamniotic twins, which stand a slim chance of survival, made even slimmer by a complication.
Under normal circumstances, twins share a womb but live in their own individual amniotic sacs. But in a monoamniotic pregnancy, which occurs in less than one percent of twin pregnancies in the United States, the twins share the same sac.