What is the relevance of serum Alpha-Fetoprotein (AFP) in monitoring fetal health in a pregnant woman taking lacosamide?

Relevance of Serum AFP in Monitoring Fetal Health During Lacosamide Treatment

Serum Alpha-Fetoprotein (AFP) testing remains a critical screening tool for detecting neural tube defects and should be performed in pregnant women taking lacosamide, as it provides essential information about fetal health that cannot be obtained through other routine prenatal tests. 1

Role of AFP in Fetal Development and Screening

• AFP is an alpha globulin synthesized initially by the yolk sac and later predominantly by the fetal liver, passing into the fetal bloodstream and eventually into maternal circulation in much lower concentrations 2
• AFP serves as a primary screening marker for open neural tube defects (ONTDs), with detection rates of 95% or greater for anencephaly and 75-90% for open spina bifida using a 2.0 MoM cutoff level 2
• Maternal serum AFP screening should be performed between 15-20 weeks gestation for optimal detection of neural tube defects 2

Clinical Significance in Pregnancy with Lacosamide

• Abnormal AFP levels (both high and low) can predict serious birth defects or adverse pregnancy outcomes, making this test particularly important for women taking medications during pregnancy 2
• Elevated maternal serum AFP is strongly associated with open neural tube defects in the fetus, requiring confirmatory testing and genetic counseling as recommended by the American College of Medical Genetics 1
• Low AFP values may be associated with chromosomal abnormalities including Down syndrome, which should be considered in the interpretation of results 2

Interpretation Considerations

• AFP results should be interpreted in the context of patient history (including medication use like lacosamide), gestational age, and other clinical factors 1
• When maternal serum AFP is elevated, confirmatory testing is required, including repeat testing if elevation is minimal, and referral for level II ultrasound and genetic counseling 1
• False-positive results may occur due to:
  • Incorrect gestational dating 2
  • Multiple gestation 2
  • Fetomaternal transfusion from amniocentesis or natural causes 3
  • Anterior placental location during amniocentesis 3

Follow-up Protocol for Abnormal Results

• For elevated AFP results, follow-up should include:
  1. Confirmation of gestational age with ultrasound 2
  2. Repeat AFP testing if elevation is minimal 2
  3. Level II ultrasound by experienced sonographers to detect potential neural tube defects 2
  4. Amniocentesis with amniotic fluid AFP and acetylcholinesterase testing when indicated 2
  5. Genetic counseling throughout the process 1

Important Considerations for Women Taking Lacosamide

• MSAFP screening should be voluntary with informed consent, but is particularly important for women taking medications during pregnancy that might affect fetal development 2
• The patient should receive nondirective counseling regarding AFP screening early in pregnancy to make an informed decision 2
• The test should only be undertaken in conjunction with a comprehensive program that provides prompt reporting, appropriate counseling, and adequate confirmatory procedures 2

Pitfalls to Avoid

• Interpreting AFP results in isolation without considering gestational age, maternal weight, race, and presence of insulin-dependent diabetes mellitus (IDDM), which can all affect normal values 2
• Failing to establish separate normative values for different patient populations (e.g., women with IDDM tend to have lower AFP levels on average) 2
• Relying solely on AFP without confirmatory testing when results are abnormal 2
• Neglecting to provide appropriate counseling before and after testing 2

By following these guidelines, healthcare providers can appropriately utilize serum AFP testing to monitor fetal health in pregnant women taking lacosamide, potentially identifying neural tube defects or other fetal abnormalities early enough for intervention.