Ultrasound during pregnancy is an ultrasound prenatal diagnosis that allows you to solve a variety of tasks: from confirming the pregnancy to clarifying data on the condition of the fetus and mother at any gestational period. With a normal pregnancy, ultrasound is performed at least three times in each trimester. At each stage, ultrasound diagnostics pursues its own goals, and also allows you to observe the development of the fetus in dynamics.
All types of ultrasound performed during gestation are divided into screening and selective. Currently, ultrasound is an obligatory component of comprehensive pregnancy management programs in all medical institutions. The purpose of screening is to identify women with complicated pregnancy and fetal pathology that require further follow-up, including using invasive methods.
During any screening ultrasound, the gestational period is clarified, fetometric parameters are evaluated, congenital pathology of fetal development is excluded, placenta, umbilical cord and amniotic fluid are evaluated. Depending on the goals and timing of prenatal screening, there are:
Selective ultrasound during pregnancy is unscheduled, additional studies prescribed for certain indications. They can be carried out at any time and in any quantities. Thus, selective ultrasound may be required to differentiate uterine and ectopic pregnancy in the early stages, with threatened miscarriage, multiple pregnancies, isthmic-cervical insufficiency, placenta previa, abnormal amount of amniotic fluid (low or polyhydramnios), with suspicion of frozen pregnancy, intrauterine hypoxia, fetal development delay, etc.
By the nature of the diagnostic information and the resulting image, the following types of ultrasound during pregnancy are distinguished:
In the early stages (in the first 12-14 weeks of gestation) Ultrasound can be performed both for the purpose of establishing pregnancy and as part of the screening of the first trimester. With the help of transvaginal scanning, it is possible to confirm pregnancy already, starting from 4-5 weeks, (when performing ultrasound with transabdominal access – for about 6-7 weeks of gestation). At the same time, ultrasound is used to determine the place of attachment of the fetal egg, to exclude ectopic pregnancy and vesicular drift.
At 11-14 weeks of pregnancy, the first screening ultrasound is performed. The main objectives of this study are: diagnostics of single or multiple pregnancies, clarification of the gestational age of the fetus (measurement of CT – coccygeal-parietal size), determination of the embryo attachment site, evaluation of extraembryonic organs (chorion, yolk sac, amnion), detection of intrauterine malformations, determination of fetal heart rate. At the same time, the pelvic organs of a pregnant woman are evaluated to detect diseases that may pose a threat to pregnancy (uterine abnormalities, fibroids, cysts and ovarian tumors, inflammatory pathology, etc.).
At this time, ultrasound during pregnancy is combined with biochemical screening – determination of the level of specific markers – hCG and RARP-A, indicating the likelihood of severe genetic disorders in the fetus (Down syndrome, Edwards syndrome, Patau syndrome, Turner syndrome, etc.). The most important fetometric indicators that allow us to judge the presence or absence of congenital pathology in the fetus are the thickness of the collar fold and the length of the nasal bone. The results of biochemical screening are compared by an obstetrician-gynecologist with ultrasound data. Based on the results of complex ultrasound and biochemical screening, the risk of having a child with genetic abnormalities is calculated. With a high degree of risk, a woman is offered an additional diagnosis – a biopsy of chorionic villi or amniocentesis.
If the ultrasound of the first trimester of pregnancy did not reveal any abnormalities in the development of the fetus and the health of the expectant mother, then the next scheduled echographic examination awaits the woman in the next trimester.
The recommended time for screening ultrasound of the second trimester is 18-21 weeks of gestation. The main purpose of this examination is the prenatal diagnosis of severe congenital malformations of the fetus. During the screening process, the specialist determines the position of the fetus, performs detailed fetometry and compares the size of the fetus with its gestational age, assesses the condition of the placenta (its location, thickness and degree of maturity), the amount of amniotic fluid, the state of the internal pharynx of the cervix and other important indicators. If a delay in fetal development is suspected, ultrasound is repeated after 2-3 weeks.
Also, during ultrasound during pregnancy at this time, you can find out the sex of the unborn child. Sometimes sex determination is of important medical importance, for example, when predicting hereditary diseases linked to sex in the fetus (hemophilia, Duchenne muscular dystrophy, etc.). When diagnosing multiple pregnancies, ultrasound helps to consider the position of fetuses relative to each other to exclude such pathology as “Siamese twins”.
Biochemical screening of the second trimester includes a triple test: determination of alpha-fetoprotein (AFP), HCG and free estriol. The most informative analysis is carried out at 16-18 weeks (no later than the 20th week). The presence of echographic signs of chromosomal pathology and a deviation in the level of serum markers is the basis for invasive prenatal diagnostics: amniocentesis, cordocentesis, placentocentesis. If congenital malformations or hereditary pathology are detected in the fetus, according to the results of cytogenetic examination of biopsy material, a medical consultation consisting of a geneticist, ultrasound diagnostics doctor, obstetrician-gynecologist, neonatologist and other specialists may recommend a woman to terminate pregnancy for medical reasons. However, the final decision remains with the pregnant woman and her family members.
The third mandatory ultrasound during pregnancy is performed at 30-34 weeks. At this time, late-manifesting malformations are detected, a functional assessment of the fetal condition is performed. The stages of the study include determining the position and the adjacent part of the fetus, assessing the size of the fetus and their compliance with gestational age, visualization of internal organs, evaluation of fetal motor activity, examination of the placenta and the amount of amniotic fluid. As a rule, planned ultrasound of the third trimester is supplemented by dopplerometry of the vessels of the uteroplacental basin, which allows to exclude fetal hypoxia.
Sometimes an additional ultrasound examination is performed 1-2 weeks before the expected date of delivery. It is performed in cases where the doctor needs to clarify the position and presentation of the fetus, its estimated birth weight, to exclude the entanglement of the umbilical cord around the neck of the child. According to the results of ultrasound during pregnancy in the third trimester, the optimal tactics of delivery is determined – independent delivery or cesarean section.
Early pregnancy ultrasound is carried out not only to obtain information about the condition of the fetus or possible pathologies, but also to confirm the fact of conception. In obstetric practice, ultrasound plays a dominant role in determining, monitoring the course of gestation, and diagnosing pathologies at the earliest stages. After the detection of conception,…
