American Journal of Obstetrics & Gynecology
Volume 199, Issue 4 , Pages 421.e1-421.e7, October 2008

Increased neonatal mortality among normal-weight births beyond 41 weeks of gestation in California

Presented at the 28th Annual Meeting of the Society for Maternal–Fetal Medicine, Dallas, TX, Jan. 28–Feb. 2, 2008.

  • Tim A. Bruckner, PhD

      Affiliations

    • Division of Epidemiology, University of California, Berkeley, School of Public Health, Berkeley, CA
    • Corresponding Author InformationReprints: Tim A. Bruckner, 50 University Hall, #7360, Berkeley, CA 94704-7360
    • ,
  • Yvonne W. Cheng, MD, MPH

      Affiliations

    • Division of Epidemiology, University of California, Berkeley, School of Public Health, Berkeley, CA
    • Division of Maternal–Fetal Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, School of Medicine, San Francisco, CA
    • ,
  • Aaron B. Caughey, MD, PhD

      Affiliations

    • Division of Maternal–Fetal Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, School of Medicine, San Francisco, CA

Received 27 February 2008; received in revised form 3 April 2008; accepted 22 May 2008. published online 18 July 2008.

Objective

The purpose of this study was to examine whether postterm gestational age increases the risk of neonatal mortality.

Study Design

We retrieved data from 1,815,811 liveborn infants in California from 1999 to 2003. We excluded multiple births and congenital anomalies, as well as infants with a gestational age of less than 38w0d, or greater than 42w6d, weeks. We used multivariable logistic regression models to adjust for demographic variables thought to confound the association.

Results

Compared to infants born at 38, 39, or 40 weeks, those born at 41w0d to 42w6d have a greater odds of neonatal mortality (aOR: 1.34, 95% CI, 1.08-1.65). Subdividing by gestational week, infants delivered at 41w0d to 41w6d showed elevated mortality relative to earlier term births (aOR: 1.37, 95% CI, 1.08-1.73). Additional analyses support this increased neonatal mortality across all normal birthweight categories.

Conclusion

Infants born beyond 41w0d of gestation experience greater neonatal mortality relative to term infants born between 38w0d and 40w6d.

Key words: neonatal mortality, placental insufficiency, postterm

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 Cite this article as: Bruckner TA, Cheng YW, Caughey AB. Increased neonatal mortality among normal-weight births beyond 41 weeks of gestation in California. Am J Obstet Gynecol 2008;199:421.e1-421.e7.

 Dr Bruckner is supported by the Ruth L. Kirschstein National Research Service Award (T-32) within the Agency for Health Care Research and Quality. Dr Caughey is supported by the National Institute of Child Health and Human Development, Grant HD01262, as a Women's Reproductive Health Research Scholar and by the Robert Wood Johnson Foundation as a Physician Faculty Scholar.

PII: S0002-9378(08)00558-9

doi:10.1016/j.ajog.2008.05.015

American Journal of Obstetrics & Gynecology
Volume 199, Issue 4 , Pages 421.e1-421.e7, October 2008

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