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Exploration and confirmation of factors associated with uncomplicated pregnancy in nulliparous women: prospective cohort study

BMJ 2013; 347 doi: https://doi.org/10.1136/bmj.f6398 (Published 21 November 2013) Cite this as: BMJ 2013;347:f6398
  1. Lucy C Chappell, clinical senior lecturer in maternal and fetal medicine1,
  2. Paul T Seed, senior lecturer in medical statistics1,
  3. Jenny Myers, clinical senior lecturer in obstetrics2,
  4. Rennae S Taylor, project manager3,
  5. Louise C Kenny, professor of obstetrics4,
  6. Gustaaf A Dekker, professor of obstetrics and gynaecology5,
  7. James J Walker, professor of obstetrics and gynaecology6,
  8. Lesley M E McCowan, professor of obstetrics and gynaecology3,
  9. Robyn A North, professor of maternal medicine1,
  10. Lucilla Poston, professor of maternal and fetal health1
  1. 1Division of Women’s Health, Women’s Health Academic Centre, King’s College London and King’s Health Partners, UK
  2. 2Maternal and Fetal Health Research Centre, Manchester Academic Health Science Centre, University of Manchester and Central Manchester Foundation Trust, UK
  3. 3Department of Obstetrics and Gynaecology, Faculty of Medical and Health Sciences, University of Auckland, New Zealand
  4. 4The Irish Centre for Fetal and Neonatal Translational Research (INFANT), Department of Obstetrics and Gynaecology, University College Cork, Republic of Ireland
  5. 5Department of Obstetrics and Gynaecology, Lyell McEwin Hospital, University of Adelaide, Australia
  6. 6Reproduction and Perinatal Health Research Group, University of Leeds, St James University Hospital, Leeds, UK
  1. Correspondence to: L C Chappell lucy.chappell{at}kcl.ac.uk
  • Accepted 4 October 2013

Abstract

Objective To identify factors at 15 and 20 weeks’ gestation associated with a subsequent uncomplicated pregnancy.

Design Prospective international multicentre observational cohort study.

Setting Auckland, New Zealand and Adelaide, Australia (exploration and local replication dataset) and Manchester, Leeds, and London, United Kingdom, and Cork, Republic of Ireland (external confirmation dataset).

Participants 5628 healthy nulliparous women with a singleton pregnancy.

Main outcome measure Uncomplicated pregnancy, defined as a normotensive pregnancy delivered at >37 weeks’ gestation, resulting in a liveborn baby not small for gestational age, and the absence of any other significant pregnancy complications. In a stepwise logistic regression the comparison group was women with a complicated pregnancy.

Results Of the 5628 women, 3452 (61.3%) had an uncomplicated pregnancy. Factors that reduced the likelihood of an uncomplicated pregnancy included increased body mass index (relative risk 0.74, 95% confidence intervals 0.65 to 0.84), misuse of drugs in the first trimester (0.90, 0.84 to 0.97), mean diastolic blood pressure (for each 5 mm Hg increase 0.92, 0.91 to 0.94), and mean systolic blood pressure (for each 5 mm Hg increase 0.95, 0.94 to 0.96). Beneficial factors were prepregnancy fruit intake at least three times daily (1.09, 1.01 to 1.18) and being in paid employment (per eight hours’ increase 1.02, 1.01 to 1.04). Detrimental factors not amenable to alteration were a history of hypertension while using oral contraception, socioeconomic index, family history of any hypertensive complications in pregnancy, vaginal bleeding during pregnancy, and increasing uterine artery resistance index. Smoking in pregnancy was noted to be a detrimental factor in the initial two datasets but did not remain in the final model.

Conclusions This study identified factors associated with normal pregnancy through adoption of a novel hypothesis generating approach, which has shifted the emphasis away from adverse outcomes towards uncomplicated pregnancies. Although confirmation in other cohorts is necessary, this study implies that individually targeted lifestyle interventions (normalising maternal weight, increasing prepregnancy fruit intake, reducing blood pressure, stopping misuse of drugs) may increase the likelihood of normal pregnancy outcomes.

Trial registration Australian New Zealand Clinical Trials Registry ACTRN12607000551493.

Footnotes

  • We thank the pregnant women who participated; Claire Roberts for her contributions in establishing the SCOPE study in Adelaide; Denise Healy for coordinating the Australian SCOPE study; Annette Briley for coordinating the UK MAPS (SCOPE) study; Nicolai Murphy for coordinating the Cork SCOPE study; the SCOPE research midwives; Steven Wu for his assistance with data imputation; Eliza Chan for her database management and statistical help; Alistair Stewart for statistical help; and Dharmintra Pasupathy for comments on the manuscript.

  • Contributors: LCC and RAN designed this component of the SCOPE study, analysed and interpreted the data, drafted the article and revised it critically for important intellectual content, and gave final approval of the version to be published. JM, LCK, GAD, JJW, LMEMcC, and LP conceived and designed the study, interpreted the data, and critically revised the paper for important intellectual content. RST was designed the study, coordinated the clinical study, and revised the article critically for important intellectual content. PTS carried out the statistical analyses, interpreted the data, and revised the article critically for important statistical content. All authors had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis. RAN is guarantor. RAN and LP are joint senior authors.

  • Funding: This study was funded by New Enterprise Research Fund, Foundation for Research Science and Technology; Health Research Council (04/198); Evelyn Bond Fund, Auckland District Health Board Charitable Trust; Premier’s Science and Research Fund, South Australian Government; Guy’s and St Thomas’ Charity, Tommy’s Charity; UK National Health Services (NEAT grant FSD025), University of Manchester Proof of Concept Funding, National Institute for Health Research; Health Research Board, Ireland (CSA/2007/2). JM is supported by an Action Medical research endowment fund and Manchester Biomedical Research Centre. The study funders had no role in the study design, data analysis, or writing of this report.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare that RAN, LMEMcC, JM, GAD, LP, RST, and LCK declare their institutions received money to fund the SCOPE study including some salary component (except for GAD).

  • Ethical approval: This study was approved by the local ethics committees (New Zealand AKX/02/00/364, Australia REC 1712/5/2008, London and Manchester 06/MRE01/98 and Cork ECM5 (10) 05/02/08) and all the women provided written informed consent.

  • Data sharing: Additional data are available from RAN on request (robyn.north{at}kcl.ac.uk).

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