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An outcome-based approach for the creation of fetal growth standards: do singletons and twins need separate

K S Joseph1, John Fahey, Robert W Platt

  • 1Perinatal Epidemiology Research Unit, Department of Obstetrics and Gynaecology and of Pediatrics, Dalhousie University and the IWK Health Centre, Halifax, Nova Scotia, Canada. ksjoseph@dal.ca

American Journal of Epidemiology
|January 8, 2009
PubMed

Insights

Separate fetal growth standards are needed for twins and singletons. Optimal birth weight ranges, minimizing neonatal risks, differ significantly between twin and singleton infants, supporting plurality-specific standards.

Area of Science:

  • Perinatology
  • Neonatal Health
  • Biostatistics

Background:

  • Current fetal growth standards rely on theoretical percentile distributions.
  • The need for distinct growth standards for singleton and twin pregnancies remains debated.

Purpose of the Study:

  • To determine if separate fetal growth standards are required for singletons versus twins.
  • To identify optimal birth weight ranges associated with minimal neonatal morbidity and mortality.

Main Methods:

  • Utilized an outcome-based methodology on a large dataset of US livebirths (1995-2002).
  • Analyzed singleton and twin livebirths between 36 and 42 weeks' gestation (n=17,811,922).
  • Identified birth weight ranges with the lowest rates of serious neonatal morbidity and mortality.

Main Results:

  • Optimal birth weight ranges for minimizing neonatal risks were identified for both singletons and twins.
  • The lower limit of the optimal birth weight range was significantly lower for twins compared to singletons (152g difference).
  • Minor variations in optimal birth weight were noted based on maternal factors, but plurality was a key differentiator.

Conclusions:

  • Birth weight-specific morbidity and mortality patterns support the necessity of plurality-specific fetal growth standards.
  • Current theoretical standards may not adequately represent the optimal growth trajectory for twin infants.
  • Clinical guidelines should consider distinct fetal growth references for singleton and twin pregnancies.

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