Low birth weight a risk for babies?
August 10, 2007
SUMMIT COUNTY ” While Frisco resident Traci Kennedy was pregnant, she ate well, gained the recommended amount of weight and received good prenatal care.
However, when her son Caden was born on Dec. 22 at Summit Medical Center, he weighed just 5 pounds 7 ounces, classifying him as a low birth weight infant.
At first, Caden appeared to be healthy. But his little body struggled during the first night to regulate his blood sugar, which began to plummet early the next morning.
The Flight for Life ground crew rushed him to The Children’s Hospital in Denver, where he was placed on a glucose drip. After three days, Caden’s physicians took him off the I.V. and sent him home to gain weight. He’s now doing well and up to a normal weight.
A high rate of low birth weight babies has plagued Colorado for at least half a century. According to the Colorado Department of Public Health and Environment, 9.1 percent of babies born in the state from 2003-2005 were of low birth weight, one of the highest rates in the country.
In Summit County, the numbers are even grimmer: 10.3 percent of babies born are low birth weight, which is more than double the federal Healthy People 2010 goal of 5 percent. In Eagle County, that rate is 8.7 percent.
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The national average lies around 8 percent of births.
Low birth weight, defined as weighing 5 pounds 8 ounces or fewer at birth, can cause a host of problems for newborns. It can contribute to infant mortality, as well as neurological and developmental deficits. Several studies have demonstrated an association between low birth weight and obesity and hypertension later in life.
A variety of factors have been associated with low birth weight. In a 2000 report, the state health department compiled data from birth certificates across the state to determine which of those variables contributed most significantly to Colorado’s low birth weight rate.
Inadequate weight gain during pregnancy topped the list. During the years preceding the report, one in four pregnant women in Colorado failed to gain an adequate amount of weight.
A focus group pulled together by the department of health showed that women who didn’t gain enough weight during pregnancy fell into two basic groups: those who purposely restricted their weight gain, and those who didn’t have access to healthy foods and were unaware of the nutritional requirements of pregnancy, said Sue Ricketts, maternal and child health demographer at the state health department.
Unlike standard weight gain guidelines given to previous generations of women, newer standards, developed by the Institute of Medicine in 1990, recommend different amounts of gain depending on a woman’s pre-pregnancy body mass index, or BMI. For example, a woman with a normal BMI should gain about 25-35 pounds, while an underweight woman may need to gain 28-40 pounds. An obese woman may need to gain just 15 pounds.
But the focus group also revealed that many women never received counseling from their physicians about the appropriate amount of weight to gain.
“Not enough physicians use these guidelines,” Ricketts said. “They tend to go with a generic one size fits all approach, and that’s not the right way to do it.”
Smoking closely followed inadequate weight gain as a major risk factor associated with low birth weight, according to the state health department report. If all pregnant women in Colorado gained adequate weight and did not smoke during pregnancy, the state’s low birth weight rate would decrease by one-quarter.
While the state and county health departments acknowledge that altitude can decrease birth weight, but some experts don’t consider it an excuse.
Ricketts pointed out that high altitude regions also exist in Utah, but the state’s low birth weight rate is much lower than Colorado’s, though fewer people live at high altitude in Utah and the Mormon Church helps keep residents well-nourished.
Still, altitude is a factor.
Researchers have studied the effects of altitude on pregnancy for decades. On average, every 3,300 feet of elevation gained reduces fetal weight by about 3.5 ounces, according to a 1997 study in Colorado. So in Summit County, with an average elevation of about 9,000 feet, babies could on average be born about 10 ounces lighter than those born at sea level.
Local pediatrician Dr. Chris Ebert-Santos said most newborns she sees in Summit County are born around 6 pounds, instead of the national average of 7-8 pounds.
Fetuses at altitude grow more slowly than those at lower elevations, said Lorna Moore, a professor at the Altitude Research Center at the University of Colorado at Denver and Health Sciences Center, who co-authored the 1997 altitude study. Some of altitude’s contribution to low birth weight is understood and documented, but much of the explanation remains elusive.
“The reason that babies grow more slowly, we think, is that there is less oxygen available in utero,” Moore said. But exactly what that reduction in oxygen does to the growing fetus is still under question.
In Summit County, more women develop pregnancy-related blood pressure issues and preeclampsia than at lower altitudes, which can affect fetal growth, said Dr. Julie Gelman, an obstetrician-gynecologist with High Country Health Care. But Gelman also sees inadequate weight gain, smoking and other factors contributing to low birth weight.
“It’s so rare that people with no other risk factors have a small baby just because they live here,” she said.
Pregnancy-related altitude effects in Colorado can be difficult to document, because a relatively small portion of the population lives at 8,000 feet or above ” where the effects really begin to kick in.
But studies in more heavily populated and even higher elevation regions, such as Bolivia, have demonstrated that altitude exudes a very real influence on fetal growth. For example, studies controlling for other factors, including smoking, socio-economic status and preeclampsia, have associated altitude independently with low birth weight.
It would be difficult to attribute Caden Kennedy’s low birth weight solely to altitude. But altitude did play a major role in his first eight weeks of life. Like at least half of infants born in Summit County, Caden’s low oxygen saturation after birth required him to be placed on full-time oxygen during that time.
A developing fetus receives oxygen through the placenta at a lower concentration than exists in the air, pediatrician Ebert-Santos said.
When a baby is born and takes its first breath, the higher concentration of oxygen in the air sparks a process that converts the baby’s lungs into breathing machines. At altitude, babies typically receive enough oxygen just after birth, because even up here, the oxygen level in the air is considerably higher than the baby is accustomed to in the womb.
But between a day and two weeks later, the baby’s oxygen saturation often begins to dip, and the baby starts needing supplemental oxygen to make a smooth transition into the world. Most babies acclimate within two months.
Some of them don’t.
Liliana Grace Head was born May 7 at Summit Medical Center. After birth, her oxygen saturation began to drop, and her physician placed her on oxygen. Liliana’s parents, Erin and Brandon Head, who lived at 9,800 feet in Breckenridge, were prepared.
But at Liliana’s two-month check-up, her oxygen saturation had dropped to 73 percent, falling considerably short of the normal level of 89-93 percent. At that point, conversations with their pediatrician shifted from supplement oxygen to the newborn to the possibility of long-term consequences from an oxygen deficit, such as heart murmurs and pulmonary problems.
The Heads sprung into action, selling their house and moving to the low altitude state of Minnesota. Within 45 minutes of landing in Minnesota, Erin brought the baby to the doctor to check her oxygen levels: 97 to 99 percent.
“Problem solved,” Brandon said.
Only a small percentage of babies don’t acclimate to the conditions at altitude. But there’s no guarantee which ones will.
“It is a gamble as to whether the kids can handle it,” he said.