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Changes in parental smoking during pregnancy and risks of adverse birth outcomes and childhood overweight in Europe and North America: An individual participant data meta-analysis of 229,000 singleton births.

The Generation R Study Group, Erasmus University Medical Center, Rotterdam, the Netherlands. Department of Pediatrics, Sophia Children's Hospital, Erasmus University Medical Center, Rotterdam, the Netherlands. Department of Pediatrics, New York University School of Medicine, New York City, New York, United States of America. Department of Environmental Medicine, New York University School of Medicine, New York City, New York, United States of America. Department of Population Health, New York University School of Medicine, New York City, New York, United States of America. New York Wagner School of Public Service, New York City, New York, United States of America. New York University College of Global Public Health, New York City, New York, United States of America. Subdirección de Salud Pública Gipuzkoa, San Sebastián, Spain. Instituto de Investigación Sanitaria BIODONOSTIA, San Sebastián, Spain. CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain. EPIUnit-Instituto de Saúde Pública, Universidade do Porto, Porto, Portugal. Department of Public Health and Forensic Sciences and Medical Education, Unit of Clinical Epidemiology, Predictive Medicine and Public Health, University of Porto Medical School, Porto, Portugal. Research Institute, Department of Pediatrics, Marien-Hospital Wesel, Wesel, Germany. Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. Centre for Occupational and Environmental Medicine Stockholm County Council, Stockholm, Sweden. Born in Bradford, Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Bradford, United Kingdom. Centre for Behavioural Science and Mental Health, Istituto Superiore di Sanità, Rome, Italy. Cork Centre for Vitamin D and Nutrition Research, School of Food and Nutritional Sciences, University College Cork, Cork, Ireland. Irish Centre for Fetal and Neonatal Translational Research, Cork University Maternity Hospital, University College Cork, Cork, Ireland. Université de Paris, CRESS, INSERM, INRA, Paris, France. Department of Preventive Medicine, University of Southern California, Los Angeles, United States of America. Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environment et travail)-UMR_S 1085, Rennes, France. First Department of Pediatrics, National and Kapodistrian University of Athens Medical School, Aghia Sophia Children's Hospital, Athens, Greece. Department of Environmental Exposure and Epidemiology, Norwegian Institute of Public Health, Oslo, Norway. Maine-Dartmouth Family Medicine Residency, Augusta, Maine, United States of America. MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, United Kingdom. Department of Exposure and Environmental Epidemiology, Norwegian Institute of Public Health, Oslo, Norway. The Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy. Department of Epidemiology, Lazio Regional Health Service, Rome, Italy. Department for Health Evidence, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, the Netherlands. Radboud REshape Innovation Center, Radboud University Medical Center, Nijmegen, the Netherlands. Department of Social Medicine, University of Crete, Heraklion, Greece. NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom. Department of Environmental Epidemiology, Nofer Institute of Occupational Medicine, Lodz, Poland. Center for Global Health, University of Illinois College of Medicine, Chicago, Illinois, United States of America. Department of Statistics and Computational Research, Universitat de València, València, Spain. Department of Health Security, Finnish Institute for Health and Welfare, Kuopio, Finland. Department of Obstetrics and Gynaecology, Cork University Maternity Hospital, Cork, Ireland. Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden. Sachs' Children and Youth Hospital, Stockholm, Sweden. MRC Integrative Epidemiology Unit at the University of Bristol, Oakfield House, Oakfield Grove, Bristol, United Kingdom. Population Health Science, Bristol Medical School, University of Bristol, Bristol, United Kingdom. Department of Environmental Immunology/Core Facility Studies, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany. Division of Health Data and Digitalization, Norwegian Institute of Public Health, Oslo, Norway. Department of Nutrition and Dietetics, School of Health Science and Education, Harokopio University, Athens, Greece. Department of Epidemiology, Care and Public Health Research Institute, Maastricht University Maastricht, the Netherlands. National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark. Department of Public Health, Section of Epidemiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Department of Dietetics, Nutrition and Sport, School of Allied Health, Human Services and Sport, La Trobe University, Melbourne, Australia. Paediatrics & Child Health, University College Cork, Cork, Ireland. Research Unit for Gynaecology and Obstetrics, Institute for Clinical Research, University of Southern Denmark, Denmark. Department of Population Medicine, Harvard Medical School, Harvard Pilgrim Health Care Institute, Boston, Massachusetts, United States of America. Department of Public Health, Amsterdam Public Health Research Institute, Academic Medical Center, Amsterdam, the Netherlands. Department of Environmental Exposures and Epidemiology, Domain of Infection Control and Environmental Health, Norwegian Institute of Public Health, Oslo, Norway. Department of Public Health, University of Helsinki, Helsinki, Finland. Department of Medical Sciences, University of Turin, Turin, Italy. Unit of Epidemiology, "Anna Meyer" Children's University Hospital, Florence, Italy. The Novo Nordisk Foundation Center for Basic Metabolic Research, Section on Metabolic Genetics, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Institute of Epidemiology, Helmholtz Zentrum München-German Research Center for Environmental Health, Neuherberg, Germany. Norwegian Institute of Public Health, Oslo, Norway. Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway. ISGlobal, Institute for Global Health, Barcelona, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Spain. Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University Munich, Munich, Germany. Ib-salut, Area de Salut de Menorca, Palma, Spain. Bradford Institute for Health Research, Temple Bank House, Bradford Royal Infirmary, Duckworth Lane, Bradford, United Kingdom. Department of Medical and Social Problems of Family Health, Institute of Pediatrics, Obstetrics and Gynecology, Kyiv, Ukraine.

PLoS medicine. 2020;(8):e1003182
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Abstract

BACKGROUND Fetal smoke exposure is a common and key avoidable risk factor for birth complications and seems to influence later risk of overweight. It is unclear whether this increased risk is also present if mothers smoke during the first trimester only or reduce the number of cigarettes during pregnancy, or when only fathers smoke. We aimed to assess the associations of parental smoking during pregnancy, specifically of quitting or reducing smoking and maternal and paternal smoking combined, with preterm birth, small size for gestational age, and childhood overweight. METHODS AND FINDINGS We performed an individual participant data meta-analysis among 229,158 families from 28 pregnancy/birth cohorts from Europe and North America. All 28 cohorts had information on maternal smoking, and 16 also had information on paternal smoking. In total, 22 cohorts were population-based, with birth years ranging from 1991 to 2015. The mothers' median age was 30.0 years, and most mothers were medium or highly educated. We used multilevel binary logistic regression models adjusted for maternal and paternal sociodemographic and lifestyle-related characteristics. Compared with nonsmoking mothers, maternal first trimester smoking only was not associated with adverse birth outcomes but was associated with a higher risk of childhood overweight (odds ratio [OR] 1.17 [95% CI 1.02-1.35], P value = 0.030). Children from mothers who continued smoking during pregnancy had higher risks of preterm birth (OR 1.08 [95% CI 1.02-1.15], P value = 0.012), small size for gestational age (OR 2.15 [95% CI 2.07-2.23], P value < 0.001), and childhood overweight (OR 1.42 [95% CI 1.35-1.48], P value < 0.001). Mothers who reduced the number of cigarettes between the first and third trimester, without quitting, still had a higher risk of small size for gestational age. However, the corresponding risk estimates were smaller than for women who continued the same amount of cigarettes throughout pregnancy (OR 1.89 [95% CI 1.52-2.34] instead of OR 2.20 [95% CI 2.02-2.42] when reducing from 5-9 to ≤4 cigarettes/day; OR 2.79 [95% CI 2.39-3.25] and OR 1.93 [95% CI 1.46-2.57] instead of OR 2.95 [95% CI 2.75-3.15] when reducing from ≥10 to 5-9 and ≤4 cigarettes/day, respectively [P values < 0.001]). Reducing the number of cigarettes during pregnancy did not affect the risks of preterm birth and childhood overweight. Among nonsmoking mothers, paternal smoking was associated with childhood overweight (OR 1.21 [95% CI 1.16-1.27], P value < 0.001) but not with adverse birth outcomes. Limitations of this study include the self-report of parental smoking information and the possibility of residual confounding. As this study only included participants from Europe and North America, results need to be carefully interpreted regarding other populations. CONCLUSIONS We observed that as compared to nonsmoking during pregnancy, quitting smoking in the first trimester is associated with the same risk of preterm birth and small size for gestational age, but with a higher risk of childhood overweight. Reducing the number of cigarettes, without quitting, has limited beneficial effects. Paternal smoking seems to be associated, independently of maternal smoking, with the risk of childhood overweight. Population strategies should focus on parental smoking prevention before or at the start, rather than during, pregnancy.

Methodological quality

Publication Type : Meta-Analysis

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