Alpha-fetoprotein in pregnancy: why it should be measured

A protein present in the plasma of the embryo and, from the second trimester, in the maternal one, which can signal any anomalies of the fetus. But beware of false positives

Alpha-fetoprotein, also called AFP, is a protein, or more precisely a glycoprotein, present in the plasma, which is produced by the fetus in the liver, yolk sac and intestinal epithelium. It is very important to measure alpha-fetoprotein levels because, when they deviate from the norm, it can signal the presence of important birth defects in the baby. Generally, AFP levels increase significantly during the early stages of fetal development, until they can also be detected in maternal blood and amniotic fluid , approximately between the fifteenth and twentieth weeks.

What pathologies can it report

Lower or higher than average levels of alpha-fetoprotein, as we said, can signal the presence of congenital diseases, but it is essential to clarify that by themselves they only indicate a suspicion and cannot lead to a diagnosis. In particular, an excessive concentration of AFP can signal neuronal tube defects, therefore malformations of the central nervous system such as spina bifida. Values ​​lower than normal, on the other hand, can be connected to a chromosomal alteration such as trisomy 21, or Down’s syndrome . In both cases, only a further investigation consisting of ultrasound examination or amniocentesis can give an effective diagnosis.

How to measure alpha-fetoprotein

Generally, alpha-fetoprotein levels are measured in the so-called tri-test, a blood sample that can be taken from the fifteenth week of pregnancy](/fifteenth-week-of-pregnancy/). In the tri-test, in addition to AFP, the values ​​of estriol (an estrogen produced by the placenta) and gonadotropin (also called HGP, is another hormone linked to the correct development of the fetus) are also checked. It must be repeated that the level of this protein in the plasma can be an indicator of possible problems, but by itself it is never decisive. This is not only because any suspicions must be confirmed by further investigations, but also because there are numerous conditions that can taint the results of the test, making it unreliable.

What can alter the test results

There are many factors that affect the outcome of the screening and that affect the alpha-fetoprotein values ​​detected by the test, especially giving rise to false positives. Among these we point out the wrong calculation of the gestational age, cigarette smoking, the presence of twin pregnancies , gestational diabetes , placental abruption, neoplasms of the mother’s liver or uterus. Furthermore, the results of the examination must be interpreted taking into account the age of the pregnant woman, her weight and, according to some studies, her ethnicity.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

Leave a Reply

Your email address will not be published. Required fields are marked *