BOSTON (Reuters) - Obese women have a higher risk of giving birth to stillborn babies than previously thought. Although heavier women are less likely to give birth to a dangerously underweight child, "higher maternal weight before pregnancy increases the risk of late fetal death," the study said. A team of researchers of the Karolinska Institute in Stockholm, Sweden, studied pregnancy records for 167,750 women. The findings suggest that "pre-pregnancy obesity may not be as strongly protective against perinatal mortality as has been widely believed," Dr. Honor Wolfe of Wayne State University said in an editorial in the journal. The Cnatingius study found the lowest rate of stillborn births in the leanest women. Women of normal weight were twice as likely to have a stillborn baby than women who were thin. Among women who had given birth previously, the likelihood of having an underweight baby was highest among the leanest women.