This holiday season, Karen and Gregory Johnston have the best gift they could ask for -- their 6-week-old twin daughters Jessica Marie and Alyssa Renee.

The twins were born "healthy and strong" on Nov. 13 to the former Hermitage residents, who now live in Massachusetts, despite a frightening diagnosis four months ago.

On Aug. 21, 16 weeks into Mrs. Johnston's pregnancy, the couple not only found out they were having twins, they also learned that the twins might not survive. The twins were diagnosed with Twin to Twin Transfusion Syndrome, a disease of the placenta caused by unequal sharing of blood between the two fetuses.

"I never knew anything about the diagnosis until we were told we had it," Mrs. Johnston said.

The disorder causes the "recipient" twin to receive more blood and then is forced to process the extra volume through her kidneys, resulting in increased urinary output and amniotic fluid levels. This forces her heart, liver and kidneys to work much harder until her system can no longer function. The "donor" twin receives very little blood, resulting in low amniotic fluid levels, according to information provided by Mrs. Johnston.

Mrs. Johnston said the diagnosis came through a routine ultrasound performed to determine if her twins were identical or fraternal.

At the time of her diagnosis, Mrs. Johnston didn't know where to turn for information. The biggest help, she said, was the Twin to Twin Transfusion Foundation in Cleveland, which has a Web site and sent her a package of information. She also learned that December is National Twin to Twin Transfusion Syndrome month.

After the diagnosis, Mrs. Johnston's perinatologist, Dr. David Acker of the Brigham and Women's Hospital in Boston, gave her three options: terminate the pregnancy, wait it out and let the pregnancy terminate itself or consider laser photo-coagulation surgery. He recommended Dr. Rubin Quintero in Tampa, Fla., a surgeon well-known for performing this procedure.

Two days later, Mrs. Johnston flew to Tampa for the surgery.

"Dr. Quintero is one of a handful of surgeons who specialize (in the procedure) in the United States," Mrs. Johnston said. "He's trained international surgeons and doctors on the procedure."

Except for delivering the twins three months early, Mrs. Johnston had no complications from the surgery. She stayed in Tampa for two days after the surgery, then flew home to Massachusetts.

However, the Johnstons had another obstacle to overcome.

Their insurance company, Tufts Health Maintenance Organization, would not cover the procedure that would save the lives of their two babies. The company denied coverage because the surgery was considered to be experimental.

After two requests and an internal appeal, the insurance company still denied coverage, but said it would cover participation in a Twin to Twin Transfusion Syndrome Trial funded by the National Institute of Health at Children's Hospital of Philadelphia, Mrs. Johnston said. But the Johnstons and their doctor agreed this was a risky option.

"We weren't going to decide the fate of our children by a flip of the coin," Mrs. Johnston said.

So the Johnstons used every resource they had so Mrs. Johnston could undergo surgery. They charged the hospital bills, used frequent-flyer miles and Mrs. Johnston spent the second night in Tampa in a hotel instead of the hospital.

After the surgery, the Johnstons applied for an external appeal with the Massachusetts Department of Public Health Office of Patient Protection, which was sent to an independent reviewer. On Dec. 7, they received a letter from the agency saying that the insurance company's decision had been overturned.

"I really think it's important for people to stand up to big monopolies and use their strength and fight," Mrs. Johnston said. "Everything has gone our way in this case."

Now the Johnstons, along with 5-year-old daughter, Brittany, can concentrate on visiting Jessica and Alyssa in the neonatal intensive care ward at Brigham Women's Hospital.

"We visit every day. My husband and I change back and forth," Mrs. Johnston said. "On weekends we all go together."

Mrs. Johnston, who works as an intellectual property specialist with Dyax Corp. in Cambridge, said her company has been very flexible with her situation.

"They've been really good with me," she said. "I've been working irregular hours, to say the least."

This year, Mrs. Johnston said she, her husband and Brittany celebrated their "merriest Christmas ever."

"We have our miracle babies and we won the battle with the insurance company," Mrs. Johnston said. "We couldn't be happier! And if one more wish comes true out of all of this, it would be for more people to be aware of the Twin to Twin Transfusion Syndrome and for people to fight for what they deserve from monopolies like insurance companies."

For more information about Twin to Twin Transfusion Syndrome, call the Twin to Twin Transfusion Syndrome Foundation at (800) 815-9211, or log on to www.ttsfoundation.org.