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Intrauterine growth retardation: standards for diagnosis
R L Goldenberg1, G R Cutter, H J Hoffman
1Department of Obstetrics and Gynecology, University of Alabama, Birmingham 35294.
Insights
Defining intrauterine growth retardation (IUGR) varies due to inconsistent 10th percentile birth weight standards. Methodological differences in studies significantly impact these growth benchmarks.
Area of Science:
- Perinatology
- Neonatology
- Pediatric Growth Standards
Background:
- Intrauterine growth-retarded (IUGR) infants are typically defined as weighing below the 10th percentile for gestational age.
- Existing 10th percentile standards lack a uniform population basis, leading to significant variations in cutoff birth weights.
Purpose of the Study:
- To investigate the factors contributing to the variability in 10th percentile birth weight standards used for defining IUGR.
- To highlight the need for a standardized national approach to IUGR assessment.
Main Methods:
- Analysis of existing studies used to derive current 10th percentile standards for infant birth weight.
- Examination of methodological differences across studies, including population characteristics, gestational age determination, infant exclusion criteria, and control variables (sex, race, parity).
Main Results:
- Variations in 10th percentile cutoffs are influenced by differences in study populations, geographic locations, and methodologies.
- Key methodological factors include gestational age calculation, infant inclusion/exclusion criteria, study design (hospital vs. population-based), and control for infant sex and maternal factors.
Conclusions:
- Methodological variations in study design and data collection are critical determinants of 10th percentile cutoffs for IUGR.
- A single, national standard for IUGR is essential for consistent comparison of research on risk factors, diagnostics, management, and outcomes.
Abstract:
An intrauterine growth-retarded infant is commonly defined as one weighing less than the 10th percentile in birth weight for its gestational age. However, because there is no standard population from which to derive these percentiles, the birth weights that serve as the cutoff point in various published studies may differ by several hundred grams at any gestational age. For this reason, we examined the studies from which the currently used 10th-percentile standards are derived to determine which factors may be responsible for the variation. In addition to obvious differences in the populations and geographic areas on which they were based, studies differed in how gestational age was determined, whether the gestational age was "rounded" or given in completed weeks, which types of infants were excluded, whether the studies were hospital or population based, and whether they were controlled for sex of the infant and race and parity of the mother. These differences in study methodology may be as or more important than the population differences in defining the 10th percentile cutoffs. A single national standard for intrauterine growth retardation would allow comparison between studies of risk factors, diagnostic tests, management, and long-term follow-up status of fetuses and infants with intrauterine growth retardation.