SOURCES: Anne-Monique Nuyt, M.D., head, division of neonatology, Sainte-Justine University Hospital and Research Center, Montreal, and professor, pediatrics, University of Montreal; Bani Ratan, M.D., obstetrician-gynecologist, Houston Methodist Hospital; May 2015 Obstetrics & Gynecology
THURSDAY, April 9, 2015 (HealthDay News) -- Women who were born prematurely may be more likely to deliver their own babies early, a new study suggests.
Canadian researchers found that the odds of delivering a preterm infant -- born before 37 weeks of pregnancy -- rose more than 40 percent for women who were born between 32 and 36 weeks themselves, regardless of other risk factors.
What's more, the earlier in pregnancy a woman had been born, the higher the risk of a similar fate for her offspring.
"We don't know whether it's a genetic cause or something that's set differently in a woman because she was born preterm, or if it's a combination of both," said study author Dr. Anne-Monique Nuyt, head of the division of neonatology at Sainte-Justine University Hospital and Research Center in Montreal.
"I think we're clearly identifying a new at-risk population for preterm delivery," added Nuyt, who is also a professor of pediatrics at University of Montreal. "I think a woman's own [birth] history should be part of the history taken at the beginning of a pregnancy."
Nuyt cautioned that the study shouldn't lead women who were born prematurely to panic when they become pregnant.
"We don't want this to be alarmist," she said. "Even if 14.2 percent of women born before 32 weeks delivered prematurely during the study period, let's not forget that means 85 percent of them delivered at term."
Plus, the current study was only designed to find an association between a woman's prematurity and her baby's, not to prove a cause-and-effect relationship.
The findings were published in the May issue of the journal Obstetrics & Gynecology.
About 12 percent of births in the United States and nearly 9 percent in developed regions occur prematurely, according to background information in the study. The vast majority of preterm babies survive to adulthood, but the phenomenon is the leading cause of infant death and health complications in industrialized countries.
While various risk factors for premature birth have been identified, many such deliveries have no known cause. Prior research from Nuyt's team found that women born at a low birth weight, whether from prematurity or other reasons, also have greater risks of experiencing high blood pressure or diabetes while pregnant.
For the new research, Nuyt and her colleagues examined health records from about 900,000 women in Quebec who had delivered at least one baby and divided the women into groups: Those born before 32 weeks of gestation; between 32 and 36 weeks; and at term, which is approximately 40 weeks.
Overall, just over 14 percent of women who were born before 32 weeks delivered babies prematurely during the study period, as did 13 percent of those born between 32 and 36 weeks. Nearly 10 percent of women born at term delivered prematurely, according to the study.
One expert said the findings make sense.
"I'm not necessarily surprised by what the [new research] found. I think as we do more research, we're finding genetic causes for things we see as [exceptions]," said Dr. Bani Ratan, an obstetrician and gynecologist at Houston Methodist Hospital in Texas.
"We should be taking detailed histories of patients and their own deliveries," Ratan suggested, adding that she already asks her patients how large they were as newborns as a means of gauging how big or small their own babies may be.
Nuyt said further research is still needed, with a goal of preventing preterm delivery among women who had once been preemies themselves.
"We want to see the cycle stopped," she said, "so that every little girl born premature, whatever the reason, has a chance not to perpetuate this condition to the following generation."
The World Health Organization offers a fact sheet about preterm birth.