Birthweight is increasing in the United States

Area of Science:

• Perinatology and Neonatal Health
• Public Health and Epidemiology
• Reproductive Medicine

Background:

• Rising rates of maternal obesity and diabetes mellitus have coincided with increased instances of large-for-gestational-age (LGA) neonates.
• The cesarean delivery rate in the US has also increased, with LGA fetuses potentially contributing to this trend.
• This study investigates historical trends in US birthweights to understand their evolution over time.

Discussion:

• While overall mean birthweight remained stable, significant increases were observed for neonates born at 39-42 weeks gestation.
• A notable decrease in birthweight was recorded for neonates born at 37 weeks gestation, with unclear contributing factors.
• Trends in birthweight varied by race and ethnicity, with non-Hispanic Black and Hispanic groups showing higher increases at 39-42 weeks gestation compared to non-Hispanic Whites.

Key Insights:

• Birthweight has significantly increased for neonates born at 39, 40, 41, and 42 weeks gestation between 1972 and 2020.
• Birthweight at 37 weeks gestation showed a statistically significant decrease over the same period.
• Maternal factors such as increased rates of obesity and gestational diabetes mellitus are potential contributors to the observed rise in birthweight for later gestations.

Outlook:

• Increasing birthweights in later gestations may be a contributing factor to persistently high cesarean delivery rates.
• Further research is needed to elucidate the reasons for decreased birthweight at 37 weeks gestation.
• Improved accuracy in gestational age estimation, particularly with first-trimester ultrasounds, may influence future birthweight analyses.