title: Advanced maternal age increases the risk of very preterm birth, irrespective of parity: a population-based register study.
abstract: OBJECTIVE
  To investigate whether advanced maternal age is associated with preterm birth, irrespective of parity.
  
  
  METHODS
  Population-based registry study.
  
  
  METHODS
  Swedish Medical Birth Register.
  
  
  METHODS
  First, second, and third live singleton births to women aged 20 years or older in Sweden, from 1990 to 2011 (n = 2 009 068).
  
  
  METHODS
  Logistic regression analysis was used in each parity group to estimate risks of very and moderately preterm births to women at 20-24, 25-29, 30-34, 35-39, and 40 years or older, using 25-29 years as the reference group. Odds ratios (ORs) were adjusted for year of birth, education, country of birth, smoking, body mass index, and history of preterm birth. Age-related risks of spontaneous and medically indicated preterm births were also investigated.
  
  
  METHODS
  Very preterm (22-31 weeks of gestation) and moderately preterm (32-36 weeks) births.
  
  
  RESULTS
  Risks of very preterm birth increased with maternal age, irrespective of parity: adjusted ORs in first, second, and third births ranged from 1.18 to 1.28 at 30-34 years, from 1.59 to 1.70 at 35-39 years, and from 1.97 to 2.40 at ≥40 years. In moderately preterm births, age-related associations were weaker, but were statistically significant from 35-39 years in all parity groups. Advanced maternal age increased the risks of both spontaneous and medically indicated preterm births.
  
  
  CONCLUSIONS
  Advanced maternal age is associated with an increased risk of preterm birth, irrespective of parity, especially very preterm birth. Women aged 35 years and older, expecting their first, second, or third births, should be regarded as a risk group for very preterm birth.
  
  
  CONCLUSIONS
  Women aged 35 years and older should be regarded as a risk group for very preterm birth, irrespective of parity.
authors: Division of Reproductive Health, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
authors: U
authors: U
authors: Waldenström
authors: Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska University Hospital, Stockholm, Sweden.
authors: S
authors: S
authors: Cnattingius
authors: School of Health and Social Studies, Dalarna University, Falun, Sweden.
authors: L
authors: L
authors: Vixner
authors: Division of Paediatrics, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.|Department of Neonatal Medicine K78, Karolinska University Hospital, Stockholm, Sweden.
authors: M
authors: M
authors: Norman
mesh_terms: D000328:Adult; D000367:Age Factors; D005260:Female; D005865:Gestational Age; D006801:Humans; D062071:Infant, Extremely Premature; D007231:Infant, Newborn; D016015:Logistic Models; D008423:Maternal Age; D008875:Middle Aged; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology / Q000209:etiology*; D012042:Registries; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
keywords: Maternal age; parity; preterm birth