OBJECTIVE: To investigate the association between advanced maternal age and adverse pregnancy outcomes and to compare the risks related to advanced maternal age with those related to smoking and being overweight or obese.
METHODS: A population-based register study including all nulliparous women aged 25 years and older with singleton pregnancies at 22 weeks of gestation or greater who gave birth in Sweden and Norway from 1990 to 2010; 955,804 women were analyzed. In each national sample, adjusted odds ratios (ORs) of very preterm birth, moderately preterm birth, small for gestational age, low Apgar score, fetal death, and neonatal death in women aged 30–34 years (n=319,057), 35–39 years (n=94,789), and 40 years or older (n=15,413) were compared with those of women aged 25–29 years (n=526,545). In the Swedish sample, the number of additional cases of each outcome associated with maternal age 30 years or older, smoking, and overweight or obesity, respectively, was estimated in relation to a low-risk group of nonsmokers of normal weight and aged 25–29 years.
RESULTS: The adjusted OR of all outcomes increased by maternal age in a similar way in Sweden and Norway; and the risk of fetal death was increased even in the 30- to 34-year-old age group (Sweden n=826, adjusted OR 1.24, 95% confidence interval [CI] 1.13–1.37; Norway n=472, adjusted OR 1.26, 95% CI 1.12–1.41). Maternal age 30 years or older was associated with the same number of additional cases of fetal deaths (n=251) as overweight or obesity (n=251).
CONCLUSION: For the individual woman, the absolute risk for each of the outcomes was small, but for society, it may be significant as a result of the large number of women who give birth after the age of 30 years.
LEVEL OF EVIDENCE: II
The increased risk for adverse pregnancy outcomes at or beyond age 30 years is small for an individual woman, but the consequences on a population level may be substantial.
Department of Women's and Children's Health, Division of Reproductive and Perinatal Health Care, and the Department of Clinical Science and Education, Södersjukhuset (KI SÖS), Karolinska Institutet, Stockholm, and the Centre for Clinical Research, Dalarna, Falun, Sweden; and the Center for Evidence Based Practice, Faculty of Health Sciences, Bergen University College, and the Department of Clinical Science, Faculty of Medicine and Dentistry, University of Bergen, Bergen, Norway.
Corresponding author: Ulla Waldenström, PhD, Bastugtan 42, 118 25 Stockholm, Sweden; e-mail: Ulla.Waldenstrom@ki.se.
Funded by the Swedish Medical Research Council and the County of Stockholm, Stockholm, Sweden.
The authors thank all the women, midwives, and obstetricians who provided data for this study by completing the antenatal, intrapartum, and postpartum records on which the Swedish and Norwegian National Medical Birth Registers are based.
Financial Disclosure The authors did not report any potential conflicts of interest.