Participation in maternal serum screening for Down syndrome, neural tube defects, and trisomy 18 following screen-positive results in a previous pregnancy

Physiology of Alpha-Fetoprotein as a Biomarker for Perinatal Distress: Relevance to Adverse Pregnancy Outcome

The many physiologic roles of human alpha-fetoprotein (HAFP) and its correlation with perinatal distress/pregnancy outcome are rarely addressed together in the biomedical literature, even though HAFP has long been used as a biomarker for fetal birth defects. Although the well being of the fetus can be monitored by the measurement of gestational age–dependent HAFP in biologic fluid levels (serum, amniotic fluid, urine, and vaginal fluids) throughout pregnancy, the majority of clinical reports reflect largely second trimester and (less likely) first trimester testing due to regulatory clinical restrictions. However, reports of third-trimester and pregnancy term measurement of HAFP levels performed in clinical research and/or investigational settings have gradually increased over the years and have expanded our base knowledge of AFP-associated pregnancy disorders during these stages. The different structural forms of HAFP (isoforms, epitopes, molecular variants, etc.) detected in the various biologic fluid compartments have been limited by antibody recognition of specific epitopic sites developed by the kit manufacturers based on antibody specificity, sensitivity, and precision. Concomitantly, the advances in elucidating the various biologic actions of AFP are opening new vistas toward understanding the physiologic roles of AFP during pregnancy. The present review surveys HAFP as a biomarker for fetal distress during the perinatal period in view of its structural and functional properties. An attempt is then made to relate the AFP fluid levels to adverse pregnancy complications and outcomes. Hence, the present review was divided into two major sections: (I) AFP structure and function considerations and (II) the relationship of AFP levels to the distressed fetus during the third trimester and at term.

First trimester screening for aneuploidies in successive pregnancies: correlations between markers

OBJECTIVES

Screening for chromosomal abnormalities in the first trimester of pregnancy is based on maternal age, nuchal translucency (NT), and biochemical markers (pregnancy-associated plasma protein-A and free beta human chorionic gonadotrophin). We have assessed the influence of screenings and outcomes in previous pregnancies on screenings in subsequent pregnancies.

METHODS

Retrospective study of the correlation between the variables of first trimester combined screening for chromosome abnormalities in patients with subsequent pregnancies. Excluded were gestations with fetal aneuploidies.

RESULTS

Between July 1999 and December 2009, there were 2291 women with more than 1 euploid pregnancy screened in the first trimester in our hospital. There was a moderate correlation for pregnancy-associated plasma protein-A (ρ = 0.530, p <0.001) and free beta human chorionic gonadotrophin (ρ = 0.439, p <0.001) between the first and second pregnancy. The trend continued in successive pregnancies. NT showed no correlations of clinical importance. With an overall false positive (FP) rate of 2.1% for the combined screening, the probability of having a recurrent FP in the second pregnancy was 4.3% (not significant).

CONCLUSION

There are significant correlations between biochemical markers but not NT in successive pregnancies, leading to increased risk of recurrence of FP results. However, such increase is not statistically significant if the overall FP rate is very low.

Recent advances in research on alpha-fetoprotein and its clinical application

Alpha-fetoprotein (AFP) is an important marker for the diagnosis of fetal defects and tumors, especially hepatic carcinoma. However, AFP has a low specificity in the diagnosis of hepatic carcinoma. In recent years, advances in research on the mechanisms of AFP action not only lead to the discovery of many AFP-related molecules (such as AFP-L3 and AFP mRNA) that can also be used for the diagnosis of tumors, but also open up new applications of AFP in the treatment of tumors.