GRAND JUNCTION, Colo. (AP) _ A month-old baby was breathing through a ventilator as doctors worked to keep her alive after she was pulled from a car that skidded into a river. Her mother and two grandparents died in the crash.

Samantha Venable's 19-year-old father, Gabriel Rivera, said his baby, who had been submerged 45 minutes in the frigid water, was a ''real fighter who's going to make it.''

Several of his relatives were at the hospital, touching and kissing the 9- pound infant who lay with life-supporting tubes stuck in her tiny limbs.

''We were going to get married in December,'' Rivera, of Kingwood, Texas, said about his baby's mother.

''Now it's just me and the baby. I feel ... no, I believe, she will survive.''

Dr. Jim Piper said Tuesday the baby's ''short-term and long-term outlooks are in grave doubt,'' but added that she was responding to treatment.

''She seems somewhat more stable, although no one could give you a good outlook now,'' he said.

Piper said it would be impossible to estimate whether the infant will suffer long-term brain damage or other problems.

The baby remained in critical condition in the intensive care nursery of St. Mary's Hospital in Grand Junction.

The accident occurred Sunday when the car in which the family was riding skkided off a snow-packed highway near Aspen and plunged 60-feet into the Roaring Fork River.

Doctors and fire crews rappelled down the gorge on Independence Pass to reach the car.

Dr. Steve Ayers, shivering in the water, pulled the baby from the car and said she had ''no pulse, no respiration, was blue in color.''

The baby's mother, Kay Venable, 19, of Kingwood, died four hours after being pulled from the water. Her parents, Omard Harrison, 64, and his wife, Marjorie, 61, of Houston, also died.

The family was vacationing in Colorado when their car slid off icy Independence Pass into a snow bank. They then hitched a ride with two Aspen teen-agers.

After that car skidded off the road, Britt Rosen, 17, and Maelle Deschutter, 16, managed to kick out the windows in the overturned, partially submerged car, struggle to the road and call for help.

Samantha initially was brought to Aspen Valley Hospital.

''When she arrived at the hospital, the baby's body temperature was less than 50 degrees, she had no heart rate and no brain wave activity,'' said Dr. William Mitchell. ''This baby, when it arrived, was white, cold and just totally stiff.''

Dr. Hugh Macaulay, the emergency room physician, said intravenous fluids and oxygen were warmed before they were administered to the infant.

''We used hot towels, but eventually what we had to resort to was just sticking the baby in a sink of water heated up to about 100 degrees,'' Mitchell said.

The baby's father, who arrived in Grand Junction on Tuesday, works at a Houston-area country club and attends a community college.

Samantha was born Oct. 1 in Houston. ''I was going into the Air Force and get some basic training and then we'd all be together and just live,'' Rivera said.