Maternal serum alpha-fetoprotein and birth weight

Area of Science:

• Obstetrics and Gynecology
• Maternal-Fetal Medicine
• Biochemistry

Background:

• Maternal serum alpha-fetoprotein (AFP) is a biomarker used in prenatal screening.
• Understanding the relationship between AFP levels and fetal growth is crucial for accurate pregnancy monitoring.

Purpose of the Study:

• To investigate the association between maternal serum alpha-fetoprotein (AFP) levels and infant birth weight.
• To determine the impact of varying AFP levels on the incidence of low birth weight.

Main Methods:

• Analysis of maternal serum AFP levels from 16-18 weeks gestation in 4198 singleton pregnancies.
• Correlation of AFP levels with measured infant birth weights.
• Statistical analysis to assess the significance and magnitude of associations.

Main Results:

• A U-shaped association was observed between AFP levels and birth weight, with the highest mean birth weight at 0.50-0.74 times the median AFP.
• Decreasing AFP levels (<0.25 median) were associated with a 193g decrease in birth weight and increased low birth weight incidence (4% to 11%).
• Increasing AFP levels (>3.0 median) were associated with a 371g decrease in birth weight and a significant increase in low birth weight incidence (4% to 22%).

Conclusions:

• Maternal serum AFP levels demonstrate a significant negative association with birth weight, particularly at higher levels.
• The negative association between high AFP and low birth weight is a more significant finding than any minor positive association at low AFP levels.
• Low AFP levels may be influenced by factors such as gestational age overestimation, potentially leading to misinterpretation of fetal growth and delivery timing.