By Robert Preidt
Women who were older than 35, who were overweight or obese, or who smoked were at somewhat higher risk of developing blood clots during pregnancy. Medical complications such as pre-existing diabetes, varicose veins and inflammatory bowel disease were also associated with increased risk.
The findings could help doctors identify at-risk women and take measures to prevent them from developing blood clots, which can be dangerous and potentially deadly if they break free and travel to areas such as the heart, brain or lungs.
For the study, researchers analyzed data from nearly 400,000 pregnancies that occurred between 1995 and 2009.
Among new mothers, being obese was associated with a fourfold increased risk of developing a blood clot. The risk was two times higher than normal among those who had a cesarean delivery, a premature birth, bleeding in pregnancy or had given birth three or more times, according to the study, which appeared April 2 in the journal Blood.
Women who had a stillbirth were six times more likely to develop a blood clot, formally known as venous thromboembolism (VTE).
"We believe the strong association between stillbirths and premature births and [blood clots] in particular is a finding of real importance that has received only limited attention to date," study leader Dr. Matthew Grainge, of the School of Community Health Sciences at the University of Nottingham, in England, said in a university news release. "[Stillbirths and premature births] are not currently incorporated in the guidelines for risk assessment for [blood clots] and, if they were, then many cases associated with those risk factors could potentially be prevented."
Blood clots affect about one or two pregnancies per 1,000, according to the news release. Despite being rare, blood clots are a leading cause of death in expectant and new mothers in developing countries.
"Preventative measures for [blood clots], such as a daily dose of the blood thinner heparin, may not be cost effective or safe and are therefore only recommended for women who are considered high risk," Grainge said. "However, there is currently inconsistency and disagreement over the factors that put women in that high-risk category, and we hope this research will provide clinicians with valuable new information."