TUESDAY, July 17, 2012 (HealthDay News) -- Marijuana use prior to her pregnancy greatly raises a woman's risk of premature birth, according to a study that identified the most common risk factors for preterm delivery.
"Some of these risk factors can be reduced," noted one expert, Dr. Martin Chavez, chief of maternal-fetal medicine at Winthrop-University Hospital in Mineola, N.Y. "In this particular study, it seems evident that the use of marijuana prior to becoming pregnant more than doubles one's risk of a preterm birth." Chavez was not involved in the research.
Babies who are born prematurely -- at least three weeks before their due date -- can face life-threatening health issues and are at increased risk for health problems such as diabetes and heart disease later in life, the researchers said.
In this study, researchers looked at more than 3,000 pregnant women in Adelaide, Australia, and Auckland, New Zealand. They found that a strong family history of low-birth-weight babies was the strongest risk factor for preterm birth -- increasing the risk nearly sixfold.
This was followed by factors that more than doubled the risk: use of marijuana prior to pregnancy, a mother with a history of pre-eclampsia (high blood pressure during pregnancy), a mother with a history of vaginal bleeds, and a mother with type 1 or type 2 diabetes.
The researchers also found that the greatest risk factors for preterm rupture of membranes leading to birth include: mild hypertension not requiring treatment (almost 10 times increased risk), family history of recurrent gestational diabetes (eight times increased risk), receiving some forms of hormonal fertility treatment (almost four times increased risk), and having a body-mass index of less than 20 (more than double increased risk).
The study was published online July 17 in the journal PLoS One.
"Our study has found that the risk factors for both forms of preterm birth vary greatly, with a wide variety of health conditions and histories impacting preterm birth," lead author Dr. Gus Dekker, professor of obstetrics and gynecology at the University of Adelaide, said in a university news release.
Chavez said every woman can help reduce the odds of premature delivery.
"Better outcomes can be achieved by healthier lifestyles even prior to becoming pregnant," he said. "As we try to reduce the rate of preterm delivery for our patients, all possible contributing factors should be considered, particularly the ones that can be easily eliminated."
Dekker added that the new findings may also put researchers "another step forward in potentially developing a test -- genetic or otherwise -- that will help us predict with greater accuracy the risk of preterm birth. Our ultimate aim is to safeguard the lives of babies and their health in the longer term."
The U.S. National Institute of Child Health and Human Development has more about preterm labor and birth.