DALLAS — Doctors are planning an attempt this spring to gradually separate 3-year-old twin girls who were born connected at the head.

For the past 2 1/2 years, Anastasia and Tatiana Dogaru, who are from Italy but are of Romanian descent, have been in Dallas, brought here by the World Craniofacial Foundation about nine months after their birth to be evaluated for separation surgery.

The top of Tatiana’s head is attached to the back of Anastasia’s. Twins born joined at the head — called craniopagus twins — are extremely rare, occurring in about 1 in 2.5 million births.

The separation carries many risks — including the possibility of brain damage, stroke, or a deadly amount of blood loss — but doctors say the twins cannot continue to live as they are. Not only is it awkward, but their conjoined condition would lead to a variety of medical problems.

“Without separation, the girls won’t make it,” said Dr. Kenneth Salyer, the plastic surgeon who founded the World Craniofacial Foundation and serves as chairman of the board. “And with separation, it’s a high-risk operation.”

The twins and their parents will travel in April to Rainbow Babies & Children’s Hospital in Cleveland, Ohio, where a team of doctors will separate the girls in stages.

The twins spend their days much like any other young girls: dressing up like princesses, coloring, drawing, playing house, and reading books. They easily get around their Dallas apartment with Anastasia leading the way as Tatiana follows.

“Like every mom, I want just normal kids,” said their mother, Claudia Dogaru, 31. She said that right now, the girls — who are speaking English and Romanian — are developmentally on target.

Not only do the girls share numerous of blood vessels, but Anastasia — the larger twin — has no kidney function and relies on Tatiana’s kidneys.

Separating their blood vessels is likely to take four stages, so Anastasia will have to begin dialysis. After recovering for a couple of months after the separation, Anastasia will then undergo a kidney transplant, with one of her parents being the likely donor.

As the process begins to separate their blood vessels, doctors will be watching to make sure that Tatiana’s venous drainage system — which does not function as well as her sister’s — begins operating as it should.

“Unless we can see that happen, Tatiana could not survive the separation,” said Dr. Arun Gosain, a member of the team that will separate the girls and chief of pediatric plastic surgery at Rainbow Babies & Children’s Hospital and medical director for the Rainbow Craniofacial Center. In that case, doctors will need to re-evaluate the surgery, since the objective is for both girls to survive, he said.

Doctors say that it appears the girls only share a small portion of brain matter. Before their final separation, the girls will have had skin expanders placed in their heads to make sure there’s enough to cover their brains once they are separated, Dr. Gosain said.

Since the girls arrived in Dallas, the World Craniofacial Foundation has been paying their living expenses and providing therapies. The Dogaru family sought out the foundation after hearing about the successful separation in 2003 of Egyptian conjoined twins. The boys, who were joined at the tops of their heads, were brought to Dallas by the foundation and separated at Children’s Medical Center Dallas.