title: The associations of birth intervals with small-for-gestational-age, preterm, and neonatal and infant mortality: a meta-analysis.
abstract: BACKGROUND
  Short and long birth intervals have previously been linked to adverse neonatal outcomes. However, much of the existing literature uses cross-sectional studies, from which deriving causal inference is complex. We examine the association between short/long birth intervals and adverse neonatal outcomes by calculating and meta-analyzing associations using original data from cohort studies conducted in low-and middle-income countries (LMIC).
  
  
  METHODS
  We identified five cohort studies. Adjusted odds ratios (aOR) were calculated for each study, with birth interval as the exposure and small-for-gestational-age (SGA) and/or preterm birth, and neonatal and infant mortality as outcomes. The associations were controlled for potential confounders and meta-analyzed.
  
  
  RESULTS
  Birth interval of shorter than 18 months had statistically significant increased odds of SGA (pooled aOR: 1.51, 95% CI: 1.31-1.75), preterm (pooled aOR: 1.58, 95% CI: 1.19-2.10) and infant mortality (pooled aOR: 1.83, 95% CI: 1.19-2.81) after controlling for potential confounding factors (reference 36-<60 months). It was also significantly associated with term-SGA, preterm-appropriate-for-gestational-age, and preterm-SGA. Birth interval over 60 months had increased risk of SGA (pooled aOR: 1.22, 95% CI: 1.07-1.39) and term-SGA (pooled aOR: 1.14, 95% CI: 1.03-1.27), but was not associated with other outcomes.
  
  
  CONCLUSIONS
  Birth intervals shorter than 18 months are significantly associated with SGA, preterm birth and death in the first year of life. Lack of access to family planning interventions thus contributes to the burden of adverse birth outcomes and infant mortality in LMICs. Programs and policies must assess ways to provide equitable access to reproductive health interventions to mothers before or soon after delivering a child, but also address underlying socioeconomic factors that may modify and worsen the effect of short intervals.
authors.forename: Naoko
authors.initials: N
authors.lastname: Kozuki
authors.forename: Anne C C
authors.initials: AC
authors.lastname: Lee
authors.forename: Mariangela F
authors.initials: MF
authors.lastname: Silveira
authors.forename: Cesar G
authors.initials: CG
authors.lastname: Victora
authors.forename: Linda
authors.initials: L
authors.lastname: Adair
authors.forename: Jean
authors.initials: J
authors.lastname: Humphrey
authors.forename: Robert
authors.initials: R
authors.lastname: Ntozini
authors.forename: Robert E
authors.initials: RE
authors.lastname: Black
authors.forename: Joanne
authors.initials: J
authors.lastname: Katz
mesh_terms: D000328:Adult; D001721:Birth Intervals; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007182:Income; D007223:Infant; D007226:Infant Mortality / Q000639:trends*; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D008297:Male; D008423:Maternal Age; D016017:Odds Ratio; D011247:Pregnancy; D047928:Premature Birth / Q000401:mortality*; D015995:Prevalence; D012959:Socioeconomic Factors