Continuing medical studies about the effect of altitude on birth weight point to differing conclusions that will only perpetuate the scientific debate.
"I've delivered two, almost 8-pound babies who are now healthy, intelligent teenagers," said Cindy Corbin, supervisor of the obstetrics department at Leadville's St. Vincent General Hospital, the nation's highest. "If you talk to some people, they would tell you that's almost impossible at 10,000 feet."A study completed last year in Leadville found babies born there average 6 pounds, 13 ounces, said Stacy Zamudio, a doctoral student in anthropology at the University of Colorado. That compares with an average birth weight at sea level of 7 pounds, 8 ounces.
The puzzle is why Tibetan babies, born 2,000 feet higher than Leadville, are close to the average weight of infants delivered at sea level. Yet babies born at 14,000 feet in Bolivia and Peru weigh at least a pound less.
The study is scheduled to focus on Tibet beginning in May 1991, with conclusions years off - and then likely to be challenged by the rigors of scientific inquiry.
"Some people, including doctors who practice at high altitude, don't really believe the Leadville babies are smaller, because it's a subtle effect," Zamudio said.
Based on preliminary findings in a study of 500 Leadville births between July 1986 and July 1990, compared with 500 Denver births, the Leadville infants weighed an average of 3 ounces less, said Dr. John Perna, a family practitioner in Leadville.
"It's hard to tell with differences that are so small," Perna said. "The question is whether there is more risk at high altitude. The answer is still out. We know there is a slightly lower birth weight. There may be a slightly increased risk."
Another perspective is that of Dr. Paul Winchester, who founded the neonatal intensive-care unit at Memorial Hospital in Colorado Springs.
"I think there ought to be a sign on top of Pikes Peak that says, `If you're pregnant, you don't belong here," Winchester said. "But pregnancy is a time when women have a compulsion to go traveling because they know that, after they become a mother, they will never go by themselves again."
Because most of a baby's major organs are formed by the time a woman realizes she is pregnant, even a woman "who intends to do right by her baby" may cause the fetus irrevocable stress from oxygen deprivation by being at high altitude, he said.
"Babies born in Colorado Springs are even slightly smaller than those born in Denver because it's higher," he said.
Genetic differences that have evolved over millenniums may explain why Tibetan women are able to provide the infants they carry with more oxygen, Zamudio said. Archeological evidence indicates that people have lived in the Andes only about 10,000 years, implying there has not been sufficient time for evolution to work its course.
The Tibetan women may have evolved ways to transport oxygen better, and that is important to fetal growth," she said.