At 7 months old, identical twin sisters Kensley and Berkley are rolling over and making a lot of noise. The only visible clue that these are not your average babies is their size. Kensley is 13 pounds while Berkley weighs 11. Even in the womb Kensley has always been bigger -- a fact that once threatened both babies' lives.
"Medically, these babies, should not be here, and miraculously they are," said mother, Laura Ballard of Parker, Colo.
Kensley and Berkley survived an extremely rare, yet increasingly common, condition known as twin-to-twin transfusion syndrome, which occurs in identical twins when they are in the womb.
Laura and her husband Todd Ballard's saga began when the couple learned that after two and a half years of unsuccessfully trying to bring another child into the world she was carrying twins.
But Laura Ballard's doctor could not tell if the two shared the same placenta, so at 14 weeks she went to a specialist. The doctor told the couple that not only were the twins identical, but also might have twin-to-twin transfusion syndrome.
"Already at that time, one baby had much less than normal fluid around it, and one had a lot more. They were different in size," said Dr. Craig Stark, the couple's perinatologist.
All the blood, oxygen and nutrients that circulate within the baby are delivered through the placenta. It is essential during fetal life that this flow of nutrition and oxygen is maintained in a balanced way.
In babies suffering twin-to-twin transfusion syndrome, the placenta begins to shunt more of its blood to one baby and away from the other. Essentially, the babies' blood supplies become connected and one baby begins donating its nutrients to the other.
This is dangerous because one baby -- in the Ballards' case, Berkley -- basically stops growing and its internal organs begin to suffer. Kensley, meanwhile, began to grow faster than normal.
One of the most severe consequences of this condition is stuck-twin-syndrome, where one baby is so small that its kidneys don't develop the way they should, leaving less fluid around the baby that would help cushion it and help it exercise.
On the other hand, the other baby's growth is so fast that it often leaves the child with swelled organs and an increased likelihood of premature birth or death.
"He [the doctor] said, 'Don't Google it,' and the first thing we did when we left was Google it," Ballard said. "From there it was horrifying. I felt pretty much that there was no hope. I was so afraid and wondered at what point they would pass away, and when I would have to deliver them silently into this world."
Without treatment, both babies die 90 percent of the time.
In the past, the principal treatment for twin-to-twin transfusion syndrome has been to drain fluid from the bigger baby to try to allow improved balance. The hope is that the increased balance in the blood flow that the placenta provides will help both, but the success rate has been variable. Laura Ballard tried that method unsuccessfully four times.
Dr. F. Sessions Cole of Washington University in St. Louis said that in instances like the Ballards' there is little a parent can do to avoid the condition.