NEW YORK (WABC) -- New research from Sweden suggests that even slightly elevated blood pressure during late pregnancy many increase the possibility of having an underweight or stillborn infant.
The study found women with prehypertension at 36 weeks of pregnancy had about 70 percent greater odds for low birth weight or stillbirth compared to women with normal blood pressure.
The U.S. Centers for Disease Control and Prevention say infants with low birth weight are more likely to have health problems than normal-weight babies.
In this particular study, posted online in the journal Hypertension, lead researcher Dr. Anna-Karin Wikstrom and her colleagues collected data on more than 150,000 women listed in a Swedish obstetric database. The only women included in the study were ones who carried their babies for 37 weeks or longer, whose blood pressure never rose above 140/90 millimeter of mercury (mm Hg) and those who were having a single baby.
About 11 percent of the women in the study developed prehypertension, also referred to as borderline high blood pressure. Prehypertension is a systolic pressure (the top number) between 120 and 139 mm Hg and a diastolic pressure (the bottom number) between 80 and 89 mm Hg, or both.
Wikstrom, an associate professor of obstetrics at Uppsala University in Sweden, said women with a diastolic blood pressure increase of 15 points or more and developed prehypertension were more likely to have an underweight baby.
Research also showed a rise in diastolic blood pressure, even if it didn't reach prehypertension, still increased the risk of low birth weight. In this scenario, the likelihood of low birth rate increased 2 percent for every point.
The researchers stressed that their study showed only an association between blood pressure and fetal outcomes, not a cause-and-effect relationship.