Nov. 13, 2003 -- Having first and second babies fathered by dif
Nov. 13, 2003 -- Having first and second babies fathered by different men may double a woman's risk for giving birth to her second child prematurely or having other labor and delivery problems, new research from Norway suggests.
The study showed that women who changed fathers between their first two pregnancies had higher rates of preterm deliveries and low-birth-weight babies than those who had the same partner for both pregnancies. Infant mortality for the second birth was also greater for women who switched partners.
Lead researcher Lars J. Vatten, MD, tells WebMD that the association is most likely explained by a higher incidence of risky behaviors among women who have multiple sex partners. In a separate analysis, they found that women who switched partners between the first and second child may have different behaviors that increase the risk of adverse events during pregnancy. For instance, they found that these women were more likely to smoke.
"I think this is the main underlying factor here, but it is probably not the only one," Vatten says. "We can't really be sure why this occurs, but with a divorce rate approaching 50% it is something that probably deserves further study."
Twice the Risk
Using national birth registry data from 1967 to 1998, Vatten and colleague Rolv Skjaerven identified 31,683 Norwegian women who changed partners between their first two births and 456,458 women who had the same partners for both births. The researchers adjusted for several other risk factors that might effect pregnancy, labor, and delivery, such as maternal age and education, but they were unable to include lifestyle factors such as smoking and drinking because they were not included in the registry at the time.
Women with multiple partners were roughly twice as likely to go into preterm labor and deliver low-birth-weight infants during their second pregnancy. They were also at a higher risk of infant death. The findings are reported in the Nov. 15 issue of the British Medical Journal.
However, these women had only a slightly increased risk of having a problem during the first pregnancy and delivery. While this argues against the risky lifestyle theory, Vatten says it could also mean that the total time that a woman engages in risky behaviors plays a part in risk.
"We saw a substantial increase in risk among these women, and it seems likely that lifestyle differences are involved," he says.
'Biggest Lifestyle Risk Factor'
Ob-gyn Robert Welch, MD, calls cigarette smoking the biggest lifestyle risk factor for problem deliveries because so many women continue to smoke while pregnant. Welch leads the ob-gyn department at Providence Hospital, near Detroit, and is a spokesman for the American College of Obstetrics and Gynecology.
A review of almost 70,000 Norwegian births since 1998 found that women who had different partners for their first and second children were three times as likely to smoke as women who had the same partner for both births.
"Cigarette smoking is still an epidemic," Welch tells WebMD. "We know that smoking definitely increases the risk for preterm birth, stillbirth, and other adverse pregnancy outcomes. Fewer women may be smoking during pregnancy, but many still are."
