Cross-Country Individual Participant Analysis of 4.1 Million Singleton Births in 5 Countries with Very High Human Development Index Confirms Known Associations but Provides No Biologic Explanation for 2/3 of All Preterm Births

• Published in: PloS one 2016-09, Vol.11 (9), p.e0162506-e0162506
• Main Authors: Ferrero, David M, Larson, Jim, Jacobsson, Bo, Di Renzo, Gian Carlo, Norman, Jane E, Martin, Jr, James N, D'Alton, Mary, Castelazo, Ernesto, Howson, Chris P, Sengpiel, Verena, Bottai, Matteo, Mayo, Jonathan A, Shaw, Gary M, Verdenik, Ivan, Tul, Nataša, Velebil, Petr, Cairns-Smith, Sarah, Rushwan, Hamid, Arulkumaran, Sabaratnam, Howse, Jennifer L, Simpson, Joe Leigh
• Format: Article
• Language: English
• Subjects: Age; Analysis; Biology and Life Sciences; Birth; Birth rate; California - epidemiology; Childbirth & labor; Children & youth; Childrens health; Czech Republic - epidemiology; Data processing; Databases, Factual; Developed Countries; Epidemiology; Female; Gynecology; Health aspects; Health risks; Humans; Income; Infant mortality; Infant, Newborn; Infants; Intervention; Male; Maternal & child health; Medical research; Medicin och hälsovetenskap; Medicine; Medicine and Health Sciences; Multivariate Analysis; New Zealand - epidemiology; Obstetrics; Obstetrics, Gynecology and Reproductive Medicine; Pediatrics; People and Places; Pre-eclampsia; Preeclampsia; Pregnancy; Premature birth; Premature Birth - epidemiology; Premature Birth - prevention & control; Premature infants; Public health; Regression Analysis; Reproductive technologies; Reproduktionsmedicin och gynekologi; Risk analysis; Risk Factors; Sex; Slovenia - epidemiology; Socioeconomic factors; Sweden - epidemiology; Variation; Womens health
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0162506

Preterm birth is the most common single cause of perinatal and infant mortality, affecting 15 million infants worldwide each year with global rates increasing. Understanding of risk factors remains poor, and preventive interventions have only limited benefit. Large differences exist in preterm birth rates across high income countries. We hypothesized that understanding the basis for these wide variations could lead to interventions that reduce preterm birth incidence in countries with high rates. We thus sought to assess the contributions of known risk factors for both spontaneous and provider-initiated preterm birth in selected high income countries, estimating also the potential impact of successful interventions due to advances in research, policy and public health, or clinical practice. We analyzed individual patient-level data on 4.1 million singleton pregnancies from four countries with very high human development index (Czech Republic, New Zealand, Slovenia, Sweden) and one comparator U.S. state (California) to determine the specific contribution (adjusting for confounding effects) of 21 factors. Both individual and population-attributable preterm birth risks were determined, as were contributors to cross-country differences. We also assessed the ability to predict preterm birth given various sets of known risk factors. Previous preterm birth and preeclampsia were the strongest individual risk factors of preterm birth in all datasets, with odds ratios of 4.6-6.0 and 2.8-5.7, respectively, for individual women having those characteristics. In contrast, on a population basis, nulliparity and male sex were the two risk factors with the highest impact on preterm birth rates, accounting for 25-50% and 11-16% of excess population attributable risk, respectively (p