The length of the interval between a woman's pregnancies has an important role in the health of the subsequent baby, according to a new UC San Francisco study of Latina and white women in the United States.
Findings show that either a short or a long interval is linked to low birth weight, while an intermediate interval is not. Small newborns are at increased risk of illness during the critical first few weeks of life as they adjust to life outside the womb.
"We were not surprised to find that a short period of time between pregnancies is related to low birth weight in the succeeding newborn, but the connection with a long interval was unexpected," said Elena Fuentes-Afflick, MD, a UCSF assistant professor of pediatrics who treats patients at San Francisco General Hospital.
Previous studies have looked at interpregnancy intervals in African-American and white women, but this is among the first studies to focus on Latinas, according to Fuentes, who directed the research project.
Interpregnancy intervals were defined as short, 6 months and under; intermediate, between 24 and 35 months, and long, over 35 months. Reporting earlier this week (Sunday, May 3) at the annual meeting of the Pediatric Academic Societies of America in New Orleans, Fuentes-Afflick said the good news is that a woman's behavior in this area can be modified.
"We don't know all the reasons that influence interpregnancy intervals for a woman--and this is an area where I hope we can learn more--but we believe that a woman's behavior can be changed. Appropriate health education programs can have a very positive effect on this outcome," she said.
The UCSF study used 1991 birth information from the database of the U.S. National Center for Health Statistics. Data for a group of 150,000 Latina women of Mexican-origin was compared to a corresponding group of white women, which served as a control.
The length of the interval probably is not a risk factor on its own for having a smaller baby, Fuentes-Afflick emphasized, but it can be related to several biological and behavioral factors that play a role in maternal health, which in turn influences newborn status. In the first few months after childbirth, for example, many women are still in the process of recovering from complications from the previous pregnancy. In addition, the stress of family responsibilities can influence some women to adopt poor eating habits or to increase tobacco use.
A long interval also can be linked to poor maternal health through poor nutrition, excessive weight gain, and chronic tobacco use, she said. In some cases, a long interval also is an indicator of infertility problems due to serious health complications. "How the length of the interval relates to maternal health is an area where we need to do more research," Fuentes-Afflick said.
In this study, women who had a short interpregnancy interval--in comparison to those who had an intermediate interval--were 71 more likely to have a very-low-birth-weight baby, under 3.5 pounds, and 43 percent more likely to have a moderately-low-birth-weight baby, about 3.5 to 5.5 pounds. A normal-weight baby was defined as about 5.5 to 9 pounds.
Women with a long interval were 30 percent more likely to give birth to small babies--of either very low or moderately low weight--than women with an intermediate interval between pregnancies.
Fuentes-Afflick collaborated with Nancy Hessol, MSPH, an epidemiologist in the UCSF Department of Medicine, on the study. It was supported by a grant from UC Mexus, a University of California research unit that focuses on U.S.-Mexico issues and people of Mexican descent.