High fertility rates are common in low and lower-middle income countries (LMICs). Among the 6 LMICs included in the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Global Network for Women’s and Children’s Health Research (GN), fertility rates varied from 2.9 to 6.0 births per woman. High fertility rates lead to shortened time between pregnancies, without allowing the mother to fully recover to baseline health status prior to a subsequent gestation. Short intervals between pregnancies are associated with many adverse health outcomes for the mother, including anemia, placental abruption, placenta previa and uterine rupture. Short birth intervals are also associated with adverse newborn health outcomes such as infant mortality, preterm birth, low birth weight (LBW) and congenital malformations. Conversely, long birth intervals can also be associated with adverse maternal and neonatal health outcomes, such as increased risk for induction of labor, chorioamnionitis, Caesarean delivery, preterm birth, LBW, and small for gestational age infants. The ideal timing between pregnancies associated with optimal maternal and neonatal health outcomes has not been definitively established.
The limited existing evidence on the optimal timing between pregnancies is complicated by varying methodologies used to calculate birth spacing. Birth spacing can be defined in several ways, such as the birth-to-pregnancy interval (the period from the prior live birth to the conception of the index pregnancy), the inter-pregnancy interval (the period from the prior birth, regardless of whether the pregnancy resulted in miscarriage/stillbirth/live birth, to the conception of the index pregnancy) or the inter-delivery interval (IDI; the period from the delivery of the prior live birth to the delivery of the index pregnancy). In the 2005 World Health Organization (WHO) Technical Report, an expert panel preferred birth-to-pregnancy interval to measure birth spacing. Birth-to-pregnancy interval is challenging to measure in low-resource settings where pregnancy dating is inaccurate and therefore length of gestation is difficult to determine. In order to calculate birth-to-pregnancy interval, the expert panel used delivery to delivery interval minus 9 months, thus assuming the index pregnancy resulted in a term gestation. This methodology underestimates the time between births and negates the opportunity to evaluate the effect of birth spacing on the risk of prematurity. The use of IDI might be more appropriate in low-resource settings to investigate associations between birth spacing and neonatal outcomes, without introducing the bias of unknown gestational age.
Based on limited evidence, the WHO recommends a birth-to-pregnancy interval of 24 months, corresponding to an IDI of approximately 33 months, for optimal maternal and neonatal outcomes. After the WHO 2005 Technical Meeting on birth spacing, there was a call for further research to better understand the effect of birth spacing on maternal morbidity and mortality using large datasets. In this paper, we describe IDI in a prospective, multi-country pregnancy registry from 7 research sites in 6 LMICs. We examine maternal characteristics associated with varying lengths of IDI as well as the relationship between adverse delivery and neonatal outcomes and IDI.
By: Bauserman M, Nowak K, Nolen TL, Patterson J, Patel A, Lokangaka A.