Birth spacing matters in avoiding preterm births
Women with short birth spacing between their last delivery and their next conception have shorter pregnancies, risking preterm birth.
An Ohio study on birth spacing 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.
"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,”
Emily DeFranco, DO, study co-author, maternal-fetal medicine specialist, assistant professor in the department of obstetrics and gynecology at the University of Cincinnati College of Medicine
The research conducted by DeFranco and colleagues, 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:
(1) those who had waited 18 months from delivery to conception
(2) women with spacing of 12 to 18 months from delivery to conception
(3) 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 call for a 10 percent reduction in the frequency of pregnancies that occur within 18 months of a previous birth.
U.S. Department of Health and Human Services, Office of Disease Prevention and Health Promotion Healthy People 2020 objectives.
To assess the influence of inadequate birth spacing on birth timing distribution across gestation.
Population-based retrospective cohort study using vital statistics birth records.
Singleton, non-anomalous live births ≥20 weeks to multiparous mothers, 2006–2011.
Birth frequency at each gestational week was compared following short IPIs of <6, 6–12 and 12–18 months versus referent group, normal IPI ≥18 months.
Main outcome measures
Frequency of birth at each gestational week; preterm <37 weeks; <39 and ≥40 weeks.
Of 454 716 births, 87% followed a normal IPI ≥18 months, 10.7% had IPI 12–18 months and 2.2% with IPI <12 months. The risk of delivery <39 weeks was higher following short IPI <12 months, adjOR (odds ratio) 2.78 (95% CI 2.64, 2.93). 53.3% of women delivered before the 39th week after IPI <12 months compared with 37.5% of women with normal IPI, P < 0.001. Likewise, birth at ≥40 weeks was decreased (16.9%) following short IPI <12 months compared to normal IPI, 23.2%, adjOR 0.67 (95% CI 0.64, 0.71). This resulted in a shift of the frequency distribution curve of birth by week of gestation to the left for pregnancies following a short IPI <12 months and 12–18 months compared to, birth spacing ≥18 months.
While short IPI is a known risk factor for preterm birth, our data show that inadequate birth spacing is associated with decreased gestational age for all births. Pregnancies following short IPIs have a higher frequency of birth at all weeks of gestation prior to 39 and fewer births ≥40 weeks, resulting in overall shortened pregnancy duration.
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.
The study was supported by Cincinnati Children’s Perinatal Institute and the March of Dimes Prematurity Research Center Ohio Collaborative. Center for Prevention of Preterm Birth within Cincinnati Children's Hospital Medical Center’s Perinatal Institute,
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