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Explaining the 2001-02 infant mortality increase: data from the linked birth/infant death data set

Marian F MacDorman1, Joyce A Martin, T J Mathews

  • 1Division of Vital Statistics, Centers for Disease Control and Prevention, National Center for Health Statistics, 3311 Toledo Road, Hyattsville, Maryland 20782, USA.

National Vital Statistics Reports : From the Centers for Disease Control and Prevention, National Center for Health Statistics, National Vital Statistics System
|February 17, 2005
PubMed

Insights

The U.S. infant mortality rate rose in 2002, the first increase in decades. This rise was primarily driven by more births of infants weighing less than 750 grams, impacting diverse demographic groups.

Area of Science:

  • Public Health
  • Demography
  • Neonatal Research

Background:

  • The U.S. infant mortality rate (IMR) saw its first increase in over 40 years, rising from 6.8 to 7.0 deaths per 1,000 live births between 2001 and 2002.
  • Increases in IMR were observed for very low birthweight, preterm, and very preterm infants.

Purpose of the Study:

  • To analyze the contributing factors to the increase in U.S. infant mortality between 2001 and 2002.
  • To investigate the role of changes in birthweight distribution, specifically the rise in births weighing less than 750 grams.

Main Methods:

  • Analysis of U.S. birth and death records from 2001-2002.
  • Examination of birthweight distribution shifts and their impact on overall infant mortality.
  • Evaluation of hypotheses related to reporting changes, risk profiles, and medical management.

Main Results:

  • The primary driver of the increased IMR was a shift in birthweight distribution, with a notable rise in infants born weighing less than 750 grams.
  • Increased births of infants under 750 grams occurred across non-Hispanic white, non-Hispanic black, and Hispanic women, and among mothers aged 20-34.
  • While multiple births contributed, the majority of the increase in very low birthweight infants occurred among singletons.

Conclusions:

  • The increase in infant mortality is significantly linked to a rise in births of extremely low birthweight infants (<750g).
  • Factors contributing to the increase in <750g births include demographic shifts and potentially changes in medical practices, though further research is needed.
  • The complex interplay of factors necessitates more detailed studies to fully understand and address the 2001-2002 infant mortality increase.

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