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Moms' High Hemoglobin Levels Linked To Stillbirths
November 21, 2000
CHICAGO (AP) - Women with high levels of hemoglobin in their blood early in
pregnancy may be at risk for stillbirths, a Swedish study suggests, offering a
possible clue to a tragedy that often has no known cause.
In a study of 1,400 pregnant women, those who had high hemoglobin levels early
on faced nearly double the risk of giving birth to a stillborn child - a fetus
born dead more than five months into pregnancy.
High levels of hemoglobin - an oxygen-carrying protein that gives red blood
cells pigment can be caused by cigarette smoking, which also has been linked to
stillbirths. But this study found no clear association between smoking and
hemoglobin and lacked data on what caused participants' high levels.
The findings, from Dr. Olof Stephansson and colleagues at Karolinska Institute
in Stockholm, appear in Wednesday's Journal of the American Medical Association.
Problems with the placenta and birth defects are among causes of the estimated
250,000 U.S. stillbirths each year, but more than 80,000 are due to unknown
causes. The findings suggest that closely monitoring pregnant women with high
hemoglobin levels could help prevent some of those deaths, said Dr. Nancy Green,
associate medical director of the March of Dimes, a charitable group that
supports research on birth defects and child mortality.
The study "underscores the importance of prenatal visits," said Green,
who is also an assistant professor of pediatrics and cell biology at Albert
Einstein College of Medicine in New York.
Hemoglobin levels are measured in blood tests routinely given to pregnant women
during prenatal visits. Average levels for early in pregnancy should be around
13.3 grams per deciliter, Green said. Levels linked with the increased risk -
14.6 grams per deciliter or higher - were found at visits during the 10th week
of pregnancy. High levels found later in pregnancy did not seem to increase the
risk of stillbirth.
Blood containing too much hemoglobin tends to be sticky and less able to flow
through tiny blood vessels. That could disrupt blood flow to the placenta or
developing fetus, although more research is needed to explain how high levels
might cause stillbirths, Green said.
Extremely high hemoglobin levels could be due to rare heart defects in the
mother. But those deemed high in the study also could be considered at the
uppermost limit of normal and thus might not be recognized as potentially
problematic, she said.
Anemia - abnormally low levels - is a potentially serious and far more common
pregnancy complication, and women often are advised to take iron supplements to
avoid it. Green said the amount of iron normally prescribed for pregnant women
would not cause abnormal hemoglobin increases. He cautioned that the findings
should not be interpreted to mean pregnant women should stop taking iron.
Copyright 2000 The Associated Press. All rights reserved.