Long or short intervals between pregnancies associated with poor perinatal outcomes

Intervals between pregnancies shorter than 18 months and longer than 59 months are associated with increased risk of low birth weight, preterm birth and small size for gestational age, according to an article in the April 19 issue of JAMA: The Journal of the American Medical Association.

Agustin Conde-Agudelo, M.D., M.P.H., from the Fundacisn Santa Fe de Bogota, Columbia, and colleagues conducted a meta-analysis on studies published between 1966 and 2006 to examine the association between birth spacing and the risk of adverse perinatal outcomes. The researchers identified 67 articles for this analysis, which adjusted for the mother's age and socioeconomic status and reported birth spacing and perinatal outcomes. These articles included a total of 11,091,659 pregnancies.

Infants born to women with an interval shorter than six months after their last birth had a 40 percent increased risk of preterm birth, a 61 percent increased risk of low birth weight (LBW) and a 26 percent increased risk of small for gestational age (SGA), compared to children of mothers with an interval of 18 to 23 months between pregnancies. Infants of mothers with pregnancy intervals longer than 59 months had a 20 to 43 percent greater risk of these adverse outcomes. For each month that the time between pregnancies was shortened from 18 months, the risk for preterm birth, LBW and SGA increased by 1.9, 3.3 and 1.5 percent, respectively. And for each month that the time between pregnancies was lengthened beyond 59 months, the risk for these outcomes increased by 0.6, 0.9 and 0.8 percent, respectively.

"The effects of birth spacing on perinatal health found in our study, as well as the effects of both short and long intervals on infant, child and maternal health, should furnish a strong motivating force for health personnel to provide family planning," the authors write. "The results of our systematic review could be used by reproductive clinicians around the world to advise women on the benefits of delaying a subsequent pregnancy for approximately two to five years to improve the health of both mother and the next infant."