"Fighting for Their Lives"

11/29/2007 at 12:00 PM EST

Quaid brought the babies home from a checkup at Brentwood Medical Center on Nov. 14.

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Also causing concern: the long-term effects to the twins' health may not be known for some time. "They are running all sorts of tests to determine the extent of the damage," says Buffington. "They are trying to understand what it all means."

The dire situation is far different from the joy the Quaids felt when they first learned they were expecting twins. From the start, the babies' very existence has been "a great miracle," as Dennis told PEOPLE in June. Their arrival marked the fulfillment of a long and painful journey: Using their own sperm and eggs, the couple had turned to a third party – a gestational carrier – to carry the babies after Kimberly had suffered five miscarriages in the first two years of their marriage. "I was with her during several of these miscarriages," says Buffington. "She would be so broken for weeks on end because she was losing a part of her."