The study also shows that African-American women have shorter intervals of birth spacing and higher preterm births overall.
The findings were published in ‘BJOG: An International Journal of Obstetrics and Gynaecology’ on June 4, 2014. The journal is available online at http://www.bjog.org.
“We need to place a particular focus on waiting at least 18 months before becoming pregnant again in order to minimize the potential risk for preterm births for all women,” says study co-author and maternal-fetal medicine specialist Emily DeFranco, DO, an assistant professor in the department of obstetrics and gynecology at the University of Cincinnati College of Medicine.
The study, conducted by DeFranco and colleagues at the Center for Prevention of Preterm Birth within Cincinnati Children’s Hospital Medical Center’s Perinatal Institute, studied outcomes of 454,716 live births from women with two or more pregnancies over a six-year period.
The researchers, using birth records from the Ohio Department of Health, compared the pregnancy lengths of three groups of women: those who had waited 18 months from delivery to conception (the optimal time for birth spacing identified from other studies), women with spacing of 12 to 18 months from delivery to conception and those with under 12 months from delivery to conception.
The study results, according to DeFranco, show that mothers with shorter times between birth and subsequent conception were more likely to give birth prior to 39 weeks (53.3 percent compared to 37.5 percent with the optimal 18 months of birth spacing). To define it further, all women with birth spacing of less than 12 months were twice as likely to have a preterm birth—under 37 weeks—as those who waited the optimal 18 months.
While African-American mothers had the shortest lengths of birth spacing, they still had higher number of preterm births regardless of timing.
DeFranco, who has studied birth spacing for over 5 years, says: “Any woman is at risk for having a premature baby. Eleven percent of all births are preterm and most do not have an identifiable risk factor, but those who conceive prior to 18 months after delivery increase their chances of having a premature baby.”
Due to the increased risk of premature birth and other perinatal complications with inadequate birth spacing, the U.S. Department of Health and Human Services Office of Disease Prevention and Health Promotion Healthy People 2020 objectives, call for a 10 percent reduction in the frequency of pregnancies that occur within 18 months of a previous birth.
The study was supported by Cincinnati Children’s Perinatal Institute and the March of Dimes Prematurity Research Center Ohio Collaborative.
Two additional UC faculty and Cincinnati Children’s physicians collaborated on the study: professor Louis Muglia, MD,PhD, who is the co-director of the Perinatal Institute, and Shelley Ehrlich,MD, assistant professor in the division of biostatistics and epidemiology.