title: Antenatal blood pressure for prediction of pre-eclampsia, preterm birth, and small for gestational age babies: development and validation in two general population cohorts.
abstract: OBJECTIVE
  Can routine antenatal blood pressure measurements between 20 and 36 weeks' gestation contribute to the prediction of pre-eclampsia and its associated adverse outcomes?
  
  
  METHODS
  This study used repeated antenatal measurements of blood pressure from 12 996 women in the Avon Longitudinal Study of Parents and Children (ALSPAC) to develop prediction models and validated these in 3005 women from the Southampton Women's Survey (SWS). A model based on maternal early pregnancy characteristics only (BMI, height, age, parity, smoking, existing and previous gestational hypertension and diabetes, and ethnicity) plus initial mean arterial pressure was compared with a model additionally including current mean arterial pressure, a model including the deviation of current mean arterial pressure from a stratified normogram, and a model including both at different gestational ages from 20-36 weeks.
  
  
  CONCLUSIONS
  The addition of blood pressure measurements from 28 weeks onwards improved prediction models compared with use of early pregnancy risk factors alone, but they contributed little to the prediction of preterm birth or small for gestational age. Though multiple imputation of missing data was used to increase the sample size and minimise selection bias, the validation sample might have been slightly underpowered as the number of cases of pre-eclampsia was just below the recommended 100. Several risk factors were self reported, potentially introducing measurement error, but this reflects how information would be obtained in clinical practice.
  
  
  CONCLUSIONS
  The addition of routinely collected blood pressure measurements from 28 weeks onwards improves predictive models for pre-eclampsia based on blood pressure in early pregnancy and other characteristics, facilitating a reduction in scheduled antenatal care.
  
  
  BACKGROUND
  UK Wellcome Trust, US National Institutes of Health, and UK Medical Research Council. Other funding sources for authors are detailed in the full online paper. With the exceptions of CM-W, HMI, and KMG there were no competing interests.
authors.affiliation: MRC Integrative Epidemiology Unit at the University of Bristol, Bristol BS8 2BN, UK School of Social and Community Medicine, University of Bristol, Bristol BS8 2BN, UK C.Macdonald-Wallis@bristol.ac.uk.
authors.forename: Corrie
authors.initials: C
authors.lastname: Macdonald-Wallis
authors.affiliation: Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK Centre for Statistical Methodology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Silverwood
authors.affiliation: Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK Centre for Statistical Methodology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
authors.forename: Bianca L
authors.initials: BL
authors.lastname: de Stavola
authors.affiliation: MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton General Hospital, Southampton SO16 6YD, UK.
authors.forename: Hazel
authors.initials: H
authors.lastname: Inskip
authors.affiliation: MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton General Hospital, Southampton SO16 6YD, UK National Institute for Health Research Musculoskeletal Biomedical Research Unit, University of Oxford, Oxford OX3 7LE, UK.
authors.forename: Cyrus
authors.initials: C
authors.lastname: Cooper
authors.affiliation: MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton General Hospital, Southampton SO16 6YD, UK.
authors.forename: Keith M
authors.initials: KM
authors.lastname: Godfrey
authors.affiliation: MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Crozier
authors.affiliation: MRC Integrative Epidemiology Unit at the University of Bristol, Bristol BS8 2BN, UK School of Social and Community Medicine, University of Bristol, Bristol BS8 2BN, UK.
authors.forename: Abigail
authors.initials: A
authors.lastname: Fraser
authors.affiliation: School of Medicine, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Nelson
authors.affiliation: MRC Integrative Epidemiology Unit at the University of Bristol, Bristol BS8 2BN, UK School of Social and Community Medicine, University of Bristol, Bristol BS8 2BN, UK.
authors.forename: Debbie A
authors.initials: DA
authors.lastname: Lawlor
authors.affiliation: MRC Integrative Epidemiology Unit at the University of Bristol, Bristol BS8 2BN, UK School of Social and Community Medicine, University of Bristol, Bristol BS8 2BN, UK.
authors.forename: Kate
authors.initials: K
authors.lastname: Tilling
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination; D005260:Female; D005500:Follow-Up Studies; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D008297:Male; D011159:Population Surveillance / Q000379:methods*; D011225:Pre-Eclampsia / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology* / Q000209:etiology; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology