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The impact of past pregnancy experience on subsequent perinatal outcomes

Authors

  • Jennifer A. Hutcheon,

    Corresponding author
    1. Departments of Epidemiology and Biostatistics and
      Jennifer A. Hutcheon, The Montreal Children's Hospital Research Institute, 4060 Rue Sainte Catherine Ouest Suite #205, Westmount, Quebec, Canada, H3Z 2Z3. E-mail: jennifer.hutcheon@mail.mcgill.ca
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  • Robert W. Platt

    1. Departments of Epidemiology and Biostatistics and
    2. Pediatrics, McGill University Faculty of Medicine, Montreal, Canada
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Jennifer A. Hutcheon, The Montreal Children's Hospital Research Institute, 4060 Rue Sainte Catherine Ouest Suite #205, Westmount, Quebec, Canada, H3Z 2Z3. E-mail: jennifer.hutcheon@mail.mcgill.ca

Summary

In perinatal epidemiology, the basic unit of analysis has traditionally been the individual pregnancy. In this study, we sought to explore the idea of a ‘reproductive life’-based approach to modelling the effects of reproductive exposures and outcomes, where the basic unit of analysis is a woman's entire reproductive experience. Our objective was to explore whether a first pregnancy risk factor, excess gestational weight gain, has a direct effect on the birthweight outcomes of a subsequent pregnancy, independent of the weight gain and other risk factors of the second pregnancy. A study population was created by linking the obstetric records of 1220 women who delivered their first and second offspring at a McGill University teaching hospital in Montreal, Canada. Multivariable linear and logistic regression analyses were used to model the effects of gestational weight gain above recommendation on the birthweight Z-score and risk of large-for-gestational age (LGA) subsequent offspring.

After adjusting for the risk factors of the second pregnancy, an independent effect from the first pregnancy was seen on the birthweight Z-score, (effect size OR 0.17 [95% CI 0.05, 0.28] but not risk of LGA of the second pregnancy 1.30 [95% CI 0.89, 1.89]). We concluded that a pregnancy-centred approach to research that conceptualises pregnancies as self-contained and interchangeable events may not always be appropriate, and propose that analytical methods for some perinatal research questions may need to consider a given pregnancy in the context of a woman's past reproductive experiences.

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