Inferring fetal growth restriction as rare, severe, and stable over time

Area of Science:

• Perinatal Medicine
• Neonatalogy
• Public Health

Background:

• Reduced birthweight is linked to impaired growth and survival, but fetal growth restriction (FGR) lacks a clear definition.
• Current understanding suggests FGR is common and preventable, influencing public health strategies.

Purpose of the Study:

• To define pathological FGR by estimating its characteristics based on weight-specific neonatal mortality.
• To re-evaluate the prevalence and impact of pathological FGR on neonatal mortality trends.

Main Methods:

• Utilized a model assuming birthweight has no direct causal effect on neonatal mortality.
• Estimated features of pathological FGR required to explain observed weight-specific mortality patterns.

Main Results:

• Pathological FGR affects approximately 0.5% of U.S. births at term (39-41 weeks), with up to a 220-fold increased neonatal mortality risk.
• This rare condition accounts for about half of all term neonatal deaths.
• Prevalence of pathological FGR remained stable despite a 90% decline in overall U.S. neonatal mortality over decades.

Conclusions:

• Pathological fetal growth restriction is rare and constant, possibly due to developmental errors, contrasting conventional views.
• Declines in neonatal mortality are attributed to reduced baseline mortality, not changes in pathological FGR.
• Public health efforts should shift from increasing birthweight to identifying factors that reduce overall neonatal mortality.