What is the normal range of alpha-fetoprotein (AFP) according to age and gender?

From the Guidelines

Alpha-fetoprotein (AFP) normal ranges vary significantly by age and pregnancy status, with typical values below 10 ng/mL in non-pregnant adults, and increasing progressively during pregnancy to 10-30 ng/mL in the first trimester, 30-120 ng/mL in the second trimester, and 80-400 ng/mL by the third trimester. According to the study 1, maternal serum screening programs became available to identify pregnancies at risk for open neural tube defects (ONTDs) and anencephaly, with 75% to 90% of ONTDs and 95% of anencephalics detectable by elevated maternal serum alpha-fetoprotein (MSAFP) levels. Some key points to consider when interpreting AFP levels include:

• Newborns have the highest levels, ranging from 10,000-100,000 ng/mL at birth, which rapidly decline to adult levels by age one
• During pregnancy, maternal AFP levels increase progressively, with typical values of 10-30 ng/mL in the first trimester, 30-120 ng/mL in the second trimester, and 80-400 ng/mL by the third trimester
• Elevated AFP levels in adults may indicate liver disease, certain cancers, or fetal neural tube defects during pregnancy, while abnormally low levels during pregnancy might suggest chromosomal abnormalities like Down syndrome
• Laboratory reference ranges may vary slightly between different testing methods and facilities, and the optimal time for NTD screening is at 16 to 18 weeks gestation, with testing possible between 15 and 20.9 weeks. It's also important to note that the study 1 discusses clinical guidelines for screening that complement the sections of ACMG’s Standards and Guidelines for Clinical Genetics Laboratories, and that cut-off levels for ONTD screening are 2.0 to 2.5 MoM in singleton pregnancies, and 4.0 to 5.0 MoM in twin pregnancies.

From the Research

Normal Range of Alpha-Fetoprotein (AFP) According to Age and Gender

The normal range of alpha-fetoprotein (AFP) varies according to age and gender. Here are some key points to consider:

• Adults: The mean AFP level in normal adults is around 3.04 ng/ml +/- 1.9 SD, with higher levels in men compared to women 2. AFP levels also increase with age in both men and women 2, 3.
• Reference Intervals: Reference intervals for AFP in adults have been constructed, with values of 0.60-9.30 kIU/L for persons <=40 years and 1.40-12.60 kIU/L for persons >40 years 3.
• Infants: Serum AFP levels decrease rapidly after birth, with a half-life of 5.5 days between birth and 2 weeks, 11 days between 2 weeks to 2 months, and 33 days between 2 and 4 months of age 4. It takes around 8 months for AFP levels in infants to approach adult levels 4.
• Pregnancy: Maternal serum AFP levels can be used to screen for fetal neural tube defects, with higher levels indicating an increased risk 5, 6.
• Gender Differences: Some studies have found statistically significant higher AFP levels in men compared to women 2, while others have found no gender-related differences 3.

Key Findings

• AFP levels increase with age in adults 2, 3.
• AFP levels are higher in men compared to women in some studies 2.
• Reference intervals for AFP in adults have been constructed 3.
• Serum AFP levels decrease rapidly after birth in infants 4.
• Maternal serum AFP levels can be used to screen for fetal neural tube defects 5, 6.