The missing data problem in birth weight percentiles and thresholds for "small-for-gestational-age"

Area of Science:

• Perinatal epidemiology
• Fetal growth research

Background:

• Weight-for-gestational-age charts traditionally define small-for-gestational-age infants using livebirth data.
• These charts have significant limitations for preterm infants due to missing in-utero fetal weight data.

Purpose of the Study:

• To address the bias in current small-for-gestational-age definitions.
• To propose methods for unbiased perinatal weight percentile calculation.

Main Methods:

• Critically evaluate existing weight-for-gestational-age chart methodologies.
• Discuss the impact of missing fetal weight data on etiologic studies.
• Recommend standard epidemiologic approaches for handling missing data.

Main Results:

• Livebirth-based references introduce considerable bias in etiologic studies of fetal growth restriction.
• Missing data on in-utero fetal weights are a major limitation, especially for preterm infants.

Conclusions:

• Standard epidemiologic methods for missing data are crucial.
• Unbiased perinatal weight percentiles are necessary for accurate fetal growth assessment.
• Improved methods will enhance understanding of fetal growth restriction risks.