A pregnancy-associated protein A in the blood (PAPP-A)

A pregnancy-associated plasma protein A (PAPP-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 α ₂ -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 concentration in the blood serum. 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 primiparous women 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.

In case of a threatening miscarriage accompanied by bleeding (8-14 weeks of pregnancy) and development of intrauterine hematomas, the volume of which 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 late gestosis, which often precedes the clinical manifestations of pre-eclampsia, 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.

Change in serum PAPP-A concentration in pathological variants of pregnancy

Type of pathology	PAPP-A
Miscarriage	↓ (I-II)
Fetal hypotrophy	↓ (I)
Fetal trisomy	↓ (I)
Diabetes	↓ (III)
Chronic hypertension	↓ (III)
Preeclampsia	↑ (III)
Premature birth	↓ (I); (III)
Postpartum hemorrhage	↑ (III)
Primarily low placentation:
Absence of complications	↑ (I-III)
Fetal abnormalities	↓ (I); ↑ (II, III)
Fetal hypotrophy	↓ (I); ↑ (II-III);
Late miscarriage	↑ (I); ↓ (II);
Prematurity	↑ (III)

Note: ↑ - increase, ↓ - decrease. The trimester of pregnancy is indicated in parentheses.

[1], [2], [3], [4], [5], [6]