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J Epidemiol Community Health 64:956-962 doi:10.1136/jech.2009.091785
  • Theory and methods

A new method of prenatal alcohol classification accounting for dose, pattern and timing of exposure: improving our ability to examine fetal effects from low to moderate alcohol

  1. N Nassar1
  1. 1Division of Population Sciences, Telethon Institute for Child Health Research, Centre for Child Health Research, University of Western Australia, Perth, Australia
  2. 2Curtin University of Technology, Centre for Developmental Health, Perth, Australia
  3. 3School of Population Health, University of Western Australia, Perth, Australia
  4. 4National Perinatal Epidemiology Unit, University of Oxford, Oxford, UK
  1. Correspondence to Colleen O'Leary, Telethon Institute for Child Health Research, PO Box 855, West Perth, WA 6872, Australia; colleeno{at}ichr.uwa.edu.au
  1. Contributors CMO'L was the primary contributor to the paper in relation to the concept and design, analysis and interpretation of data, and drafting of the article. JJK designed and ran the original cohort study from which these data arose. NN, CB and EG supervised CMO'L in the analysis of data. SRZ provided expertise in the area of psychology and the imputation analyses. All authors contributed to the interpretation of data and reviewing of the article, and provided final approval for the version to be published.

  • Accepted 7 September 2009
  • Published Online First 19 October 2009

Abstract

Background When examining the association between prenatal alcohol exposure and fetal effects, the timing and intensity of exposure have been ignored in epidemiological studies. The effect of using dose, pattern and timing of consumption (“composite” method) was investigated in this study, to examine the association between prenatal alcohol exposure and fetal effects.

Methods The composite method resulted in six categories of exposure (abstinent, low, moderate, binge <weekly, binge 1–2×/week and heavy). The odds of language delay and child behaviour problems were calculated for the composite method and then compared with an analysis using averaged estimates of <1 and 1+ drinks per day and with stratification by quantity ignoring dose per occasion. Data used for the analyses were from a 10% random sample of non-Indigenous women delivering a live infant in Western Australia (1995–1997). Participants from the 1995-1996 cohort were invited to participate in an 8-year longitudinal survey (78% response rate n=2224; 85% were followed-up at 2 years, 73% at 5 years and 61% at 8 years).

Results The effect of moderate and binge levels of exposure was only evident with the composite method; anxiety/depression following first-trimester moderate exposure (OR 2.24, 95% CI 1.16 to 4.34), and following late pregnancy moderate (aggressive behaviour OR 1.93, 95% CI 0.91 to 4.09) and binge (language delay OR 3.00, 95% CI 0.90 to 9.93) exposures. Results for heavy levels of exposure were similar with each method. The estimates for late pregnancy were imprecise due to small numbers.

Conclusion The composite method of classification more closely reflects real-life drinking patterns and better discriminates maternal drinking than the other methods, particularly low, moderate and binge levels.

Footnotes

  • Funding The Western Australian survey of health-related behaviours and events during pregnancy and early infancy was funded by grants from Healthway (the Western Australian Health Promotion Foundation (94/2705, 96/49078 and 98/8016)).

  • Competing interests None.

  • Ethics approval Ethics approval for the conduct of this study was granted by the Princess Margaret Hospital Research Ethics Committee and the WA Confidentiality of Health Information Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.