РАРР-А during pregnancy: norm and interpretation

2024 Author: Priscilla Miln | [email protected]. Last modified: 2023-12-16 00:21

PAPP-A during pregnancy - what is it about? Prenatal diagnosis is mandatory for all women who are in position and are registered in the antenatal clinic or at the perinatal center. It allows you to identify abnormalities and pathologies in the development of the fetus, the functioning of the placenta and the state of he alth of the mother. Screening is one of the many studies. One of the important indicators is PAPP-A. It belongs to metalloproteinases (zinc-containing enzymes). Most of it is produced in the outer layer of the placenta by fibroblasts.

What is PAPP-A?

Plasma protein associated with pregnancy - this is how this abbreviation stands for. It plays a key role in complex biochemical processes that affect the growth and development of the fetus, placenta, and the development of immunity. The longer the period, the higher its level in the mother's blood. A decrease in the level of PAPP-A during pregnancy may signal that there is a risk of the baby developing Edwards or Down syndrome. This fact cannot but alarm and excite parents.

However, only rely onon results of the analysis of a blood it is not necessary. Before establishing such a diagnosis, it is necessary to comprehensively evaluate other parameters that are obtained from the results of ultrasound. The optimal time to assess PAPP-A during pregnancy is the 11-13th week, the first screening just falls on the 10-14th week. This period was not chosen by chance. It is believed that at this time it is possible to obtain the most accurate information regarding the he alth of the mother and fetus. After the 14th week, the results obtained, even if there are deviations in the child, will be the same as in a he althy one.

Factors affecting the level

An experienced specialist should take into account that the following factors influence the level of PAPP-A during pregnancy:

1. Method of conceiving a child.
2. Presence of preeclampsia in a previous pregnancy and newborn weight.
3. Weight, height, bad habits (particularly smoking).
4. Having diabetes.

If a woman has at least one of the above factors, then, most likely, in the first trimester, the content of PAPP-A during pregnancy at 12 weeks will be low. In the second and third trimester, on the contrary, its level can be increased. This should be considered before paying attention to the conclusion of a specialist.

Reason for appointment

For every study during pregnancy, there is a specific prescription or indication. Studies that should indicate the risk of developing a deviation (genetic or hereditary) are carried out duringnext screening. At the end of the first trimester, a woman needs to pass a series of tests. Along with the usual ones, such as a general blood and urine test, there are both PAPP and hCG. During pregnancy, these indicators indicate a possible risk of having a baby with Down syndrome. However, relying only on blood results alone and getting upset ahead of time if they differ from the norm is not worth it.

Parents can independently undergo this analysis, for example, if the pregnant woman is not registered or does not attend the antenatal clinic. This way they can be sure that their child is he althy, or there is a risk that should be known in advance.

Risk group

There is a certain risk group, which is conditionally such, according to medical practice, which includes women:

1. Over 35 and underage pregnant.
2. Who was previously diagnosed with threatened miscarriage, regressing or miscarriage.
3. Drug or alcohol abusers.
4. Having had an infectious disease or taking illegal, strong drugs early in pregnancy.
5. Those living in unfavorable environmental conditions or working in hazardous industries.
6. Having a genetic or hereditary disease in the family.

Do not forget that even if a pregnant woman is not included in the risk group, there is still a chance of having a child with genetic disorders.

PAPP-A and HCG. Required Tests

Together with the analysis of PAPP-A during pregnancy, the level of AFP (alpha-fetoprotein), b-hCG and the content of free estradiol in the blood serum are necessarily measured. Additionally, ultrasound evaluates parameters such as:

1. Coccyx-parietal size (KTR).
2. The thickness of the collar space (collar area, or there is another term such as the width of the neck crease).
3. Presence of a nasal bone or its absence.

If PAPP-A during pregnancy at 12 weeks is normal, then other indicators should not lag behind or exceed the established limits. From the first days of conception, special attention is paid to the level of hCG (human chorionic gonadotropin). It indicates the existing malformations in the development of the fetus and the nature of the course of pregnancy.

Preparing for analysis

The content of PAPP-A in the blood during pregnancy is determined by taking a sample of blood serum for analysis. Before taking the biomaterial, a woman should prepare. It is worth refraining from eating 6 hours before the test; fatty and spicy foods are excluded from the diet. In the morning, you can drink clean water, no more than 100 ml, so that taking blood from a vein does not cause difficulties. Blood sampling should be done in the morning. It is desirable to be in a state of physical rest. For example, rest before donating blood, sit in the office for a few minutes.

You should also weigh yourself and measure your height in advance, as these indicators haveinfluence on the interpretation of the results. It is recommended that all screening tests be performed at the same clinic or laboratory. This is due to the fact that the interpretation of data in each laboratory and the established norms are different.

Transcription of readings

When receiving the results, a woman tries to independently determine how her numbers correspond to the PAPP-A norm during pregnancy. Each laboratory has its own equipment. In order for the doctor to determine whether the results are timely, it is necessary to find out in advance whether the laboratory can translate them into MoM. This is a special coefficient that allows you to eliminate the error in the interpretation of the results.

When evaluating results, clinicians usually look at borderline values. Also taken into account are the data obtained as a result of a survey of a woman to identify factors that may influence the deviation from the norm in one direction or another. The limit value of pregnancy-associated plasma protein-A (high molecular weight glycoprotein) is from 0.5 to 2 MoM. With multiple pregnancies, the upper value can reach 3.5 MoM. This indicator is generalizing for all laboratories and clinics. If the institution where the pregnant woman is tested for prenatal screening immediately provides the results to the MoM, then it will be easier for the doctor to determine whether there are abnormalities or not.

Risk in transcribing results

Some laboratories, in addition to numbers, also indicate a comment regardinga positive test result or not. If the result says “test positive”, then this means that the child has a high risk of being born with Down syndrome. In order to ascertain this, parents may be asked to undergo a specific study. They are associated with the need to take a sample of amniotic fluid, cord blood, or a biopsy of the fetal chorion. Undoubtedly, such tests can harm the baby or lead to the threat of termination of pregnancy. However, doctors say that modern technology can minimize this risk.

A "negative" test, on the contrary, can reassure parents, since the risk of having a child with genetic abnormalities is minimal. During the second screening, the results obtained are compared with the first. This serves as a basis for canceling worries if abnormalities were detected at the first screening.

Normal during pregnancy by week

Since the first serious examination of the expectant mother takes place after the 10th week of pregnancy, it will be important to know what numbers will be considered normal at this time. At the 10-11th week, the content of the protein associated with pregnancy is within the normal range from 0.46 to 3.73 mU/l. It is this result that indicates that the fetus is not in danger. If we talk about the rate of PAPP-A during pregnancy, then for a period of 11-13 weeks the numbers should be in the range of 0.79 - 6.01 mU / l, and at the 13-14th week - already 1.47-8.54 honey/l.

Deviations can indicate not only pathologies associated with the genetics of the fetus, but also riskspremature termination of pregnancy. This may be a threat of miscarriage or intrauterine fetal death. To exclude the unreliability of the data obtained, it is recommended to conduct a study in a strictly established time period. That's why the first screening at this time also includes an ultrasound, which helps determine the exact gestational age.

Exceeding the norm: what to do?

If a pregnant woman has an increased pregnancy-associated protein, PAPP-A, and other indicators are normal, then it is necessary to find out how the woman feels throughout the first trimester. In the presence of severe toxicosis or diabetes mellitus, there is a risk of exceeding the indicators. Also, the level of PAPP-A can be increased in multiple pregnancies. Therefore, do not immediately assume that the child will have genetic abnormalities.

It is important to understand that the deviation from the norm of PAPP-A during pregnancy at 13 weeks can be caused by external factors that must be taken into account when passing the analysis. It can be stress, overweight mother, conception of a child by in vitro fertilization. To confirm or refute the diagnosis, it may be necessary to retake blood serum for the study. Alternative invasive methods may also be used. The advisability of their appointment can only be judged by a geneticist who studies all the data obtained as a result of screening.

If PAPP-A is downgraded, should we panic?

If results are below normal, PAPP-Aduring pregnancy at the 12th week, it can not be increased in any way. They may be uninformative if important parameters were not taken into account as a result of the analysis. For example, weight and height were incorrectly entered. When the level of a pregnancy-associated protein is significantly reduced, this may indicate a possible genetic disorder. In particular, we are talking about:

1. Trisomy 13 (Patau syndrome, the presence of the 13th chromosome).
2. Trisomy 18 (Edwards syndrome, in which the fetus has abnormalities incompatible with life).
3. Trisomy 21 (Down's syndrome, in which the fetus is genetically laid not 46, but 47 chromosomes; an extra chromosome can be transmitted from both the father and the mother).
4. Monosomy on the X chromosome, triploidy (threatening short stature, oligophrenia, infantilism in the fetus at birth).

In case of placental dysfunction, threat of miscarriage, a decrease in PAPP-A during pregnancy at the 13th week is a signal for urgent action. Only after consultation with a geneticist can we talk about the advisability of a chorionic biopsy or amniocentesis.

Doctor's decisions

A competent obstetrician-gynecologist will not take responsibility for asserting that a deviation from the norm is an unequivocal indication for termination of pregnancy. Even if the risk of having a child with a genetic disorder is very high, this conclusion must be verified. PAPP-A alone cannot be a prerequisite for a diagnosis.

There is a lot of evidence on the net that screening results with clear abnormalities wereerroneous and were not confirmed by repeated analysis. Moreover, no one can determine how the baby will be born with a 100% probability. Specialists can only prepare parents for the fact that perhaps a special child will appear in their family. Moreover, if, according to the results of ultrasound, the fetus develops normally, and all parameters correspond to the gestational age, there are no neural tube defects, there should be no cause for concern.

Errors in results

During the prenatal diagnosis, some indicators remain conditional. In particular, the level of PAPP-A may turn out to be unreliable in 5% of cases. Most often false positive, only in 2-4% of cases the diagnosis was confirmed, and a decision was required, on which the fate of the unborn child depended. It is also worthwhile to understand that some pathologies may not affect the PAPP-A standards in any way. It can be perfect while the child is later diagnosed with some syndrome.