title: The associations of parity and maternal age with small-for-gestational-age, preterm, and neonatal and infant mortality: a meta-analysis.
abstract: BACKGROUND
  Previous studies have reported on adverse neonatal outcomes associated with parity and maternal age. Many of these studies have relied on cross-sectional data, from which drawing causal inference is complex. We explore the associations between parity/maternal age and adverse neonatal outcomes using data from cohort studies conducted in low- and middle-income countries (LMIC).
  
  
  METHODS
  Data from 14 cohort studies were included. Parity (nulliparous, parity 1-2, parity ≥ 3) and maternal age (<18 years, 18-<35 years, ≥ 35 years) categories were matched with each other to create exposure categories, with those who are parity 1-2 and age 18-<35 years as the reference. Outcomes included small-for-gestational-age (SGA), preterm, neonatal and infant mortality. Adjusted odds ratios (aOR) were calculated per study and meta-analyzed.
  
  
  RESULTS
  Nulliparous, age <18 year women, compared with women who were parity 1-2 and age 18-<35 years had the highest odds of SGA (pooled adjusted OR: 1.80), preterm (pooled aOR: 1.52), neonatal mortality (pooled aOR: 2.07), and infant mortality (pooled aOR: 1.49). Increased odds were also noted for SGA and neonatal mortality for nulliparous/age 18-<35 years, preterm, neonatal, and infant mortality for parity ≥ 3/age 18-<35 years, and preterm and neonatal mortality for parity ≥ 3/≥ 35 years.
  
  
  CONCLUSIONS
  Nulliparous women <18 years of age have the highest odds of adverse neonatal outcomes. Family planning has traditionally been the least successful in addressing young age as a risk factor; a renewed focus must be placed on finding effective interventions that delay age at first birth. Higher odds of adverse outcomes are also seen among parity ≥ 3 / age ≥ 35 mothers, suggesting that reproductive health interventions need to address the entirety of a woman's reproductive period.
  
  
  BACKGROUND
  Funding was provided by the Bill & Melinda Gates Foundation (810-2054) by a grant to the US Fund for UNICEF to support the activities of the Child Health Epidemiology Reference Group.
authors.forename: Naoko
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authors.lastname: Kozuki
authors.forename: Anne C C
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authors.forename: Mariangela F
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authors.forename: Ayesha
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authors.lastname: Vogel
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authors.forename: Wafaie
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authors.lastname: Fawzi
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authors.lastname: Humphrey
authors.forename: Lieven
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authors.lastname: Huybregts
authors.forename: Aroonsri
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authors.lastname: Ntozini
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authors.lastname: Osrin
authors.forename: Dominique
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authors.lastname: Roberfroid
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mesh_terms: D000328:Adult; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D066088:Infant Death / Q000517:prevention & control*; D007226:Infant Mortality / Q000639:trends*; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D008423:Maternal Age; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D015995:Prevalence; D012307:Risk Factors; D055815:Young Adult