Protein in serum

Protein A-associated protein A was detected in the serum of pregnant women in 1974. The protein has a molecular weight of 820,000, a tetrameric structure, a developed carbohydrate component, and a pronounced affinity for heparin. The molecule PAPP-A has a structure identical to a2-macroglobulin, which is an inhibitor of almost all known proteinases.

In pregnancy, as well as in some malignant and inflammatory diseases, there is an increase in the biosynthesis of PAPP-A, which is manifested by an increase in its serum concentration. During pregnancy, the content of PAPP-A in the blood increases thousands of times and before delivery may exceed 200 μg / ml. The concentration of PAPP-A in the serum in primiparas and in women with a history of three pregnancies and more is reduced. Quite often, with a high concentration of PAPP-A, the placenta mass is also increased. Multiple pregnancy, as a rule, is accompanied by a high content of PAPP-A in the serum. After delivery, there is a rapid decrease in the level of PAPP-A within the first 2-3 days, and then its concentration decreases by an average of 2 times every 3-4 days.

With a threatening miscarriage accompanied by bleeding( 8-14 weeks of gestation) and development of intrauterine hematomas, whose volume does not exceed 15 ml, the concentration of PAPP-A in the blood does not change significantly. In women with bleeding at 7-20 weeks of pregnancy, a low concentration of PAPP-A in the blood is detected more often than with a normal pregnancy. In addition, approximately 10% of women whose pregnancy ended with miscarriage, PAPP-A concentrations in the serum were elevated.

Virtually all women with low placenta have a less pronounced increase in PAPP-A concentrations in the blood throughout the pregnancy.

In women with a normal placenta, premature birth and fetal hypotrophy are most often observed when a low level of serum PAPP-A occurs at the 7th to 13th week of pregnancy.

At the end of pregnancy, the concentration of PAPP-A in the serum, as well as its total content in the placenta in women suffering from diabetes, is significantly lower than with a normal pregnancy. Reduction of these indicators before birth was also recorded in pregnant women with arterial hypertension in the anamnesis.

An increase in serum PAPP-A for a gestation period of 34 weeks is found in women with severe forms of late gestosis, which often precedes the clinical manifestations of preeclampsia, and is also possible with increased diastolic pressure. Often, a high content of PAPP-A in the blood for a period of 34 weeks is found in those pregnant women who subsequently have premature birth or the postpartum period is complicated by bleeding.

In normal pregnancy, the concentration of PAPP-A in the serum increases significantly from the 7th week. The increase in the concentration of PAPP-A occurs exponentially at the beginning of pregnancy, then slows down and continues until delivery.

In chromosome abnormalities of the fetus, the content of PAPP-A in the serum in the I and early II trimester of pregnancy( 8-14 weeks) is reduced in two thirds of women. The sharpest decrease in the concentration of this protein is noted in trisomy on the chromosomes 21, 18 and 13. Anomalies of sex chromosomes in the fetus are also often accompanied by a decrease in the content of PAPP-A in the serum of the pregnant woman. Changing the concentration of PAPP-A is also possible with trisomy on the chromosome 22. The predictive value of PAPP-A for the detection of fetal abnormalities is higher than the change in levels of such well-known markers as AFP, CG, trophoblastic b1-globulin, as well as unconjugated estriol and inhibin A, and is comparable to that for free p-CG.The decrease in the level of PAPP-A in chromosomal abnormalities of the fetus is most pronounced at the 10-11th week of pregnancy.

An even more drastic decrease in the concentration of PAPP-A in the blood serum of a pregnant woman is observed when the fetus has Cornelia de Lange syndrome, in which, as in trisomies in autosomes, multiple dysplasia, malformations, delayed psychomotor and physical development are observed.

Another independent pathognomonic symptom of fetal aneuploidy at the end of the first trimester of pregnancy is thickening of the occipital fold, which is revealed by ultrasound examination, however, visualization of this form of local edema of soft tissues is quite complex and subjective even with the use of modern scanner models with high resolution. It should be noted that early verification of fetal trisomies after ultrasonic or biochemical screening and subsequent karyotyping of cytotrophoblast, obtained with chorion biopsy, allows the termination of pregnancy in the first trimester. In the second trimester, fetal aneuploidy is verified by karyotyping fibroblast-like cells from the amniotic fluid.