Advanced maternal age increases the risk of very preterm birth, irrespective of parity: a population‐based register study

• Published in: BJOG : an international journal of obstetrics and gynaecology 2017-07, Vol.124 (8), p.1235-1244
• Main Authors: Waldenström, U, Cnattingius, S, Vixner, L, Norman, M
• Format: Article
• Language: English
• Subjects: Adult; Age; Age Factors; Birth; Body mass; Body mass index; Female; Gestation; Gestational Age; Health and Welfare; Humans; Hälsa och välfärd; Infant, Extremely Premature; Infant, Newborn; Logistic Models; Maternal Age; Medicin och hälsovetenskap; Middle Aged; Odds Ratio; Parity; Population studies; Population-based studies; Pregnancy; Pregnancy complications; Premature birth; Premature Birth - epidemiology; Premature Birth - etiology; preterm birth; Registries; Regression analysis; Risk Factors; Smoking; Statistical analysis; Sweden - epidemiology; Young Adult
• ISSN: 1470-0328; 1471-0528; 1471-0528
• DOI: 10.1111/1471-0528.14368

Objective To investigate whether advanced maternal age is associated with preterm birth, irrespective of parity. Design Population‐based registry study. Setting Swedish Medical Birth Register. Population 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. Main outcome measures 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. Tweetable Women aged 35 years and older should be regarded as a risk group for very preterm birth, irrespective of parity. Tweetable Women aged 35 years and older should be regarded as a risk group for very preterm birth, irrespective of parity.