The Fairfax County ambulance sped south toward Mount Vernon Hospital, carrying a premature baby who had just been born at home and was barely breathing.

Only two or three blocks from the Mount Vernon emergency room door, the ambulance driver, on instructions from the emergency admissions doctor at Mount Vernon Hospital, wheeled around and headed north toward Alexandria Hospital, six miles away.

The incident had a happy ending -- the baby, two months premature, was in critical but stable condition in the neonatal intensive-care unit at Alexandria Hospital late last week.

However, the change in destination at that point in an emergency trip left the Mount Vernon doctor puzzled, even though he had ordered it. Dr. Donald Chapman said later that he was "incredulous to find out that they were two or three blocks away" when the ambulance reversed direction. "It was beyond any reasoning to me that they would turn around at that point."

Last-minute changes of destination are not uncommon in emergency situations, said Lt. Mike Reilly, a spokesman for the Fairfax County Fire and Rescue Department. He said that the "medics followed their standard operating procedures to the letter" and that "this is a success story in my opinion."

Chapman had suggested that the baby be taken to Alexandria Hospital because Mount Vernon Hospital has no intensive-care unit for newborns -- in fact, it has no maternity unit. But he said later that he never would have turned away the ambulance had he known it was so close.

Reilly said the ambulance crew members had complete discretion to disregard the instructions of Chapman and the medic officer if they thought the child was in danger.

"They wouldn't have bypassed that hospital if they didn't feel comfortable because ultimately the decision is made by the guy who is in the ambulance," Reilly said.

"As far as we're concerned, it was a good save," said Pam Weiger, county fire department spokeswoman.

Many of the medical details of the Jan. 10 life-and-death drive have not been publicly released. The baby's parents declined to comment, according to a spokesman for Alexandria Hospital, and they could not be reached at home.

According to Weiger, a medic van was called to a home in the southeastern part of the county shortly after midnight to help with a breech birth, which is sometimes considered dangerous to both infant and mother. According to Reilly, the infant also was in cardiac arrest.

While the three-member medic crew stayed behind to assist the mother, an ambulance was called to take the baby to a hospital. Because Mount Vernon Hospital was the closest, the ambulance headed there, according to Weiger.

Meanwhile, the medic crew back at the house called Mount Vernon to let the hospital know of the tiny patient on the way.

"I was working under the assumption that there was a medical choice involved," Chapman said. "If there was a choice, I felt it was more appropriate to take the child to Alexandria Hospital" because Alexandria could stabilize the baby and perform follow-up care.