To identify pathology in the early stages of intrauterine development is helped by screening for the first trimester . This complex of diagnostic measures is aimed at assessing the rate of intrauterine development of the baby by comparing the indicators of the period of pregnancy. The procedure is mandatory and is carried out at all future mothers.
Why screening for pregnancy?
Screening during pregnancy is an obligatory procedure, during which the risk of developing abnormalities in the fetus is established. Diagnostic procedures help to identify predisposition to the development of genetic abnormalities of the fetus, to establish a discrepancy between the development of the baby's internal organs during pregnancy.
The procedure is advisory, but women never refuse to do so, knowing the significance of such studies. There are also indications, the presence of which causes the mandatory conduct of the study:
- the woman's age is more than 35 years;
- the threat of abortion ;
- spontaneous abortion in the anamnesis;
- presence of chromosomal abnormalities of the fetus in past pregnancies;
- the transferred infections on small terms;
- forced use of drugs that are contraindicated on short terms;
- presence of bad habits (alcoholism, drug addiction);
- closely related relationship of the father and mother of the baby.
Screening for the first trimester - what is it?
The first screening for pregnancy is a comprehensive examination of the mother's body. With its implementation, doctors pursue the goal of early diagnosis and further correction of fetal development abnormalities. At the same time, they evaluate the state of health of the future mother. Screening for the first trimester consists of ultrasound and a biochemical blood test for a pregnant woman. Assessment of blood indicators is carried out at the second stage, in the presence of deviations and suspicions of pathology on the basis of ultrasound results. Stages are carried out consistently, two procedures are allowed in one day.
Ultrasound screening for 1 trimester
Ultrasound in pregnancy is important. With the help of ultrasound, doctors manage to look into the mother's womb, assess the condition of the small organism, its internal organs. In the course of such a study, in the first trimester screening, doctors pay attention to anthropometric indicators, which are an indicator of the correct development of the fetus, the correspondence of the size of its body to the gestation period. When a trimester is screened, the physician draws attention to the following parameters:
- KTP (coccygeal parietal size);
- size of the fetal head;
- symmetry of the cerebral hemispheres;
- the size of long tubular bones;
- the size of the heart and the diameter of the vessels that leave it;
- localization of the stomach and other internal organs.
Biochemical Screening Trimester
Similar tests during pregnancy doctors appoint after receiving a bad result of ultrasound. Suspected the pathology on the screen of the monitor, doctors want to make sure of the objectivity of the proposed assumptions. It should be noted that this study should be carried out exclusively at a certain time of pregnancy, as the norms of the indicators directly depend on the stage of gestation. When biochemical blood test pay attention to the following indicators:
- HCG ;
- PAPP-A .
What does the first screening show?
During the first screening, doctors try to exclude possible chromosomal abnormalities. These violations do not manifest themselves in any way, their presence does not affect the condition of the pregnant woman. However, they can be identified by the characteristic changes in the appearance of the fetus and by the presence of certain markers in the blood of a future mother. Among the possible pathologies that helps to identify screening for the first trimester:
- Down syndrome - trisomy 21 chromosomes, occurs in 1 of 700 cases.
- Pathology of neural tube development (encephalocele).
- Omphalocele - for this pathology part of the internal organs is placed under the skin of the anterior abdominal wall, into the hernial sac.
- The Patau syndrome is trisomy on chromosome 13. It is rare, 1 case for 10 000 pregnancies. It is accompanied by severe damage to the internal organs. 90% of babies born with this pathology die within the first year of life.
- Edwards syndrome - trisomy on chromosome 18. It occurs in 1 of 7000 cases. Often occurs in the elderly mothers (pregnant after 35 years).
- Triploidy - the baby is diagnosed with a triple set of chromosomes, which is accompanied by multiple malformations.
- Cornelia de Lange syndrome - characterized by the development of the fetus numerous vices with the emergence of mental retardation in the future.
How is the first trimester screening done?
Screening for pregnancy in the first trimester is carried out in strict time frames. A woman is informed in advance of the time of the event. At the appointed time she comes to the consultation and first she undergoes ultrasound. This study can be transvaginal (through the vagina) or transabdominal (through the anterior abdominal wall). In general, the procedure for the patient does not differ from usual ultrasound. After receiving the results, if a pathology is suspected, a biochemical blood test is administered. The material is taken from the vein, on an empty stomach in the morning.
First screening for pregnancy - timing
To adjust themselves, to prepare in advance for the study, women are often interested in doctors when doing a screening of the first trimester. The timing of this survey is very limited - in order to obtain objective results, it should be carried out strictly in certain periods of pregnancy. The optimal for screening is the period from the first day of the 10th week of pregnancy to the 6th day of the 13th week. In most cases, the first screening for pregnancy, the dates of which are named above, are performed at 11-12 weeks gestation. At this time, the error in the calculations is minimal.
Preparing for a 1-term screening
To screen the first trimester was objective, doctors insist on compliance with the rules of preparation for the study. In the case of ultrasound, everything is simple: if it is performed by a transvaginal sensor, then no special preparation is required; if through the anterior abdominal wall - it is required to fill the bladder before the procedure of ultrasound.
Preparation for a biochemical blood test is more complex and includes:
- Compliance with diet: exclusion from the diet of citrus, seafood, chocolate.
- Refusal of fried and fatty dishes.
- Blood surrenders in the morning hours, on an empty stomach. The last meal should take place no later than 12 hours before the estimated time of analysis.
Results of screening for 1 trimester - decoding, norm
After the screening of the first trimester, the interpretation of the results is carried out exclusively by the doctor. Pregnant can not objectively evaluate the values obtained, even when comparing them with the rates of the norm. Each pregnancy has its own characteristics, therefore, the evaluation of the result should be carried out taking into account the course of gestation, its term, the state of the female body, the number of bearing fruits.
When assessing the indicators of individual development of the baby, obtained by ultrasound, doctors pay attention to the following parameters:
- KTR - the size of the fetus from the crown to the tailbone;
- length of body - the size of the body of the baby from the top to the heels;
- Head circumference;
- BDP (biparietal size) - the distance between the dark hillocks;
- TVP - the thickness of the collar space;
- Heart rate - the heart rate of the baby.
When conducting biochemical screening during pregnancy, pay attention to two main indicators:
- β-hCG-chorionic gonadotropin;
- PAPP-A is protein-A, associated with pregnancy.
Norms of screening for 1 trimester - decoding of ultrasound, table
In each individual case, doctors, when evaluating the results of ultrasound screening for the first trimester, make a correction for the individual characteristics of fetal development. Given this fact, physicians admit a slight deviation of indicators from established norms. In addition, the results of the studies can also be affected by another factor - the error in calculating the time spent by the obstetrician. Carrying out the first screening for pregnancy, the norms of which are given in the table below, the doctors first determine the exact duration of gestation.
Screening for the first trimester - deciphering the results of blood
As noted above, the study of the blood of a pregnant woman is resorted to when a pathology is diagnosed or if there is a suspicion of it with ultrasound. In this case, doctors pay attention to the following indicators:
- β-hCG -chorionic gonadotropin, a hormonal substance synthesized by chorion. With his help diagnose pregnancy in the early stages. However, he is an important indicator for only 1 trimester. Every day the concentration of hCG increases, reaching a maximum by 11-12 weeks gestation.
- PAPP-A is protein-A, associated with pregnancy. This protein compound is produced by the placenta, responsible for its normal development and functioning. After the biochemical screening of the first trimester, the results are deciphered by the doctor who is watching the pregnant woman. The values of these indicators by pregnancy time are given in the tables below.
The sex of the child at the first screening
Prenatal screening of 1 trimester does not allow to reliably determine the sex of the future baby. Given this fact, doctors do not attach much importance to this indicator. However, at the request of the mother herself, a specialist at a convenient location of the fetus can make his own assumptions regarding the sex of the fetus. In practice, they do not always coincide with reality and are often erroneous, so when the first screening is done this parameter is not taken into account.
Poor screening results for the first trimester
A poor result of screening for the first trimester is a reason for re-examination. However, it is carried out after a time, at 2 and, if necessary, in 3 trimesters. In rare cases, with poor results from several studies, physicians can insist on conducting invasive diagnostics. Already by results of these researches the decision on prolongation of pregnancy or its interruption is made. Among these diagnostic methods:
- chorionic villus biopsy;
- cordocentesis (cord blood analysis);
- amniocentesis (study of amniotic fluid).