The final stage of pregnancy is very important. At this time, it is necessary to identify pathologies dangerous to the fetus. This article will help expectant mothers to understand why this study is needed.
What it is?
Screening of the 3rd trimester of pregnancy necessarily includes ultrasound, cardiotocography and Doppler ultrasound. Only comprehensive diagnostics helps doctors understand how the pregnancy is proceeding. Also, this screening is necessary to determine the tactics of obstetrics.
With the help of ultrasound, the doctor can evaluate the anatomy of the fetus and all membranes. Also, this study determines the functioning and development of the placenta. With the help of ultrasound, you can establish the presentation of the fetus in the womb.
The heartbeat is checked using cardiotocography. This test also measures the work of the heart muscles. To conduct this study, several wires are attached to the tummy of the expectant mother. They can determine not only the number of heartbeats of the baby, but also establish the amplitude of the contractile movements of the uterus.
To carry out the interpretation of the results obtained in the future, it is very important to carry out the research correctly. For this, indicators are evaluated, which are determined both at rest and after activity. The procedure usually lasts 30-40 minutes.
With the help of a Doppler test, you can assess the functioning of the placenta. Also, this method perfectly detects signs of placental insufficiency. Doppler is a lot like a conventional ultrasound. This test detects any abnormalities in uteroplacental blood flow.
For a comprehensive assessment of the final stage of pregnancy, additional biochemical studies may be required. These include hCG, alpha-fetoprotein, specific markers for detecting Down syndrome, and placental lactogen.
Dates
Doctors recommend carrying out such a complex of diagnostics for pregnant women at 30-34 weeks pregnancy. In some cases, a slight shift in these terms is allowed. Usually, such situations occur when the expectant mother has some kind of severe diseases of internal organs or there are pronounced hormonal disorders.
Some mothers note that doctors sent them to the third screening earlier. Such a situation is possible if the obstetrician-gynecologist observing the pregnant woman has revealed any signs of deterioration in her health.
In this case, the list of analyzes can even be slightly expanded.
Who should visit?
The third screening is not done for all pregnant women. There are a number of medical indications required for a complex of diagnostics:
- Doctors recommend that all expectant mothers who become pregnant after 35 years of age must undergo screening for the 3rd trimester of pregnancy.
- Pregnant women with a burdened family history of chromosomal and genetic pathologies should also not miss this complex of diagnostics.
- Also, third trimester screening will be needed for expectant mothers who suffered from severe toxicosis in the previous weeks of pregnancy.
- If a woman carrying a baby had frequent miscarriages or difficulties with conception before the onset of a real pregnancy, then in this case, the diagnosis should not be skipped. Quite often, various chromosomal or genetic pathologies that manifest themselves in a similar way lead to spontaneous abortions.
What does it show?
In the third trimester of pregnancy, quite a few different indicators can already be identified. With the help of ultrasound, it is possible to determine not only the size of the fetal head, but also the main orthopedic disorders. Also, with the help of this study, you can fairly accurately establish its exact weight. Experienced ultrasound specialists can tell how much the baby weighs with an accuracy of several tens of grams.
With the help of cardiotocography, oxygen filling of the blood can also be determined. Decreased placental blood flow is a clear sign of such a disorder. This method also reveals hidden signs of fetal hypoxia. In some cases, this symptom may become a manifestation of the umbilical cord entanglement of the child's neck.
Doppler ultrasonography is a technique that provides doctors with information about how the fetal cardiovascular system functions. Also, with the help of this study, doctors can identify various neurological disorders. This method can also diagnose a hypoxic condition.
If the results obtained are extremely unfavorable, then in this case the doctor may suggest that the pregnant woman go to the hospital immediately. Such a forced measure will help prevent irreversible adverse consequences for both the mother and her unborn baby.
Biochemical screening significantly complements the findings of ultrasound. A build-up of alpha-fetoprotein in the blood serum can be a likely sign of the formed Down's disease, Edwards syndrome and some other genetic disorders. An increase in hCG in the blood can also be a very likely sign of genetic abnormalities.
A decrease in the concentration of gonadotropin in the blood is a physiological situation that develops at the very end of pregnancy. Nature invented it so that the process of intrauterine development ends independently and as gently as possible. The increase in this indicator in the last weeks of pregnancy is a significant reason for early hospitalization in a hospital.
Finding an excess amount of amniotic fluid is quite often a consequence of the fact that the expectant mother suffers from diabetes. Also, various infectious diseases that a pregnant woman suffers in the first two trimesters of her pregnancy can lead to the appearance of this clinical sign.
A significant increase in the abdomen in the fetus can be a manifestation of hemolytic disease or various liver pathologies. The appearance of this symptom is due to the accumulation of excess fluid in the abdominal cavity of the fetus. A decrease in the size of tubular bones is quite often a sign of dwarfism. Also, this pathology is called dwarf disease. This disease is rather difficult to treat.
What preparation is required?
It is necessary to prepare for research. Proper preparation will help you get more reliable results:
- In order to exclude inaccurate results, it is very important to follow a certain diet a week before cardiotocography and ultrasound. Dine very lightly on the eve of the study.
- The consumption of fruits, vegetables and legumes 2-3 days before the survey should be excluded. These products can lead to increased gassing. The intestinal loops swollen with gases quite often cause the appearance of echo negativity. In this case, it will not be possible to interpret the results.
- Also, 1-2 days before the study, pregnant women should exclude any physical activity. You should also not be nervous before an ultrasound scan. The mom-to-be should remain calm and in a great mood. Walking in the fresh air on the eve of the study has a good therapeutic effect.
- Many doctors recommend an ultrasound scan on an empty stomach. However, this is not necessary at all. It is better to eat a little before carrying out this examination. You can also drink water. Bladder prefilling may be required during the later stages of pregnancy.
Indicators of the norm
To assess the final stage of pregnancy, a number of indicators are considered. Compiling a comprehensive assessment requires the interpretation of several criteria at once. Many of the estimated parameters are entered into special tables that contain their normal values.
Main criteria:
- Placenta thickness - this is the main indicator that shows the development of this organ. At 32 weeks of gestation, its values are 25.3-41.6 mm. The maturity of the placenta is also determined. Normal values of this indicator at this stage of pregnancy are defined as maturity of I or II degree.
- Amniotic fluid (amniotic) water in this period of bearing a baby is 80-278 mm. The cervix is still closed at 32 weeks gestation. Its size is 30 mm or more.
- Anatomical dimensions of the fetus are very important during this period. The size of the fetal head at 32 weeks of intrauterine growth is 310-323 mm. The average weight of babies in this period of pregnancy is 1.8-2.4 kg. The abdominal circumference is 265-285 mm.
- Also, to assess the development of the skeleton, the sizes of some bones are considered.... The length of the humerus at 32 weeks of intrauterine development in the fetus is 55-60 mm. The femoral bone is somewhat longer. Its values are 60-66 mm. The total length of the fruit is usually 43-48 cm.
- Indicators of cardiotocography are evaluated in points. In the normal course of pregnancy, they are 8-12 points. Their assessment is made up of a combination of some indicators. These include: heart rate and amplitude, basal rhythm and various deviations from it, as well as the speed of propagation of pulse waves.
- If the cardiotocography indicators of the expectant mother fall in the range from 6 to 7 points, then in this case, a mandatory additional consultation with an obstetrician-gynecologist... If this value drops below 5, hospitalization may already be required.
- Doppler indicators are also very important. Normal blood flow in the uterine vessels is usually 0.34-0.59. This indicator is also called the index of resistance. The blood flow in the blood vessels of the umbilical cord is 0.5-0.74.
- Together with instrumental diagnostic methods, doctors also evaluate and biochemical screening indicators... Normal values of hCG at 32 weeks of intrauterine development of the fetus are from 2750 to 78000 mIU / ml. The norm of alpha-fetoprotein in this period of pregnancy is 100-150 units. The concentration of placental lactogen at 32 weeks of gestation is 3.2-10.1 mg / l.
These figures are fairly average. In some cases, significant deviations are possible. The results are interpreted by an obstetrician-gynecologist.
In some cases, especially if there are doubts about the development of chromosomal or genetic pathologies, a consultation with a geneticist may be required.
When do false positive results appear?
Incorrectly carried out diagnostics leads to the fact that the screening results can be considered unreliable. Quite often, multiple pregnancies lead to an incorrect interpretation of the obtained values. In this condition, the concentration of hCG in the blood increases significantly.
If the screening is not carried out within the prescribed period of pregnancy, then the results also become unreliable. Confusion can also occur with in vitro fertilization. This is largely due to a significant increase in blood gonadotropin or hCG.
In order for the doctors to consider the results of the screening correct, it is necessary to comply with all the regulated terms for performing such a study.
Delaying them can lead to overdiagnosis. In this case, mandatory monitoring of the state of pregnancy is required.
You will learn more about third trimester screening in the following video.
