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.

Types of ultrasound during pregnancy

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:

  • screening ultrasound of the first trimester (11-14 weeks)
  • screening ultrasound of the second trimester (18-21 weeks)
  • screening ultrasound of the third trimester (30-34 weeks).

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:

  • Two-dimensional (2D) ultrasound is a standard echographic examination that gives a black-and-white image in two dimensions.
  • Three-dimensional (3D) ultrasound is a three-dimensional static image of the fetus in three projections, resembling a color photograph. It allows not only to consider the “portrait” of the unborn child in detail, but also to visualize the defects of intrauterine development with greater accuracy.
  • Four-dimensional (4D) ultrasound is a three-dimensional image that allows you to observe the fetus in motion in real time.
  • Fetometry of the fetus is the determination of the size of the fetus (circumference of the head, chest and abdomen, bone length, biparietal and frontal-occipital dimensions, etc.), allowing to judge the period of pregnancy and the correspondence of fetal development to this period. Fetometry of the fetus is usually an integral part of screening ultrasound during pregnancy, but can also be performed separately.
  • Dopplerography of uteroplacental blood flow is a study of blood vessels and hemodynamics in the “mother-placenta-fetus” system. It is carried out after the 20th week of pregnancy, after the completion of the formation of the placenta.
  • Cardiotocography – simultaneous registration of fetal heart rate and contractile activity of the uterus. It is usually prescribed after the 26th week of pregnancy, used during childbirth. Allows you to evaluate and monitor the functional state of the fetus in dynamics.
  • Fetal echocardiography is a targeted examination of the fetal heart, performed when it is suspected that he has CHD, cardiac arrhythmias, determined auscultatively or according to CTG data.
  • Cervicometry is an ultrasound of the cervix, which allows timely diagnosis of isthmic-cervical insufficiency.

Ultrasound in the first trimester

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.

Ultrasound in the second 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.

Ultrasound in the third trimester

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.

Fetal Echocardiography

Fetal echocardiography is a special ultrasound technique that allows examining the morphological and functional features of the fetal heart during pregnancy. Allows even before birth, noninvasively detect congenital heart pathology. It is usually performed at 18-24 weeks of gestation. Fetal EchoCG makes it possible to assess the condition of the heart cavities, atrial septa of heart…


Cervicometry is a transvaginal ultrasound examination during pregnancy, the purpose of which is to measure the length of the cervix, assess the condition of the external and internal pharynx and cervical canal. Ultrasound of the cervix is informative for detecting isthmic-cervical insufficiency (ICI) and predicting the risk of spontaneous termination of pregnancy or premature birth.…

Fetal Phonocardiography

Fetal phonocardiography is a technique for analyzing cardiac activity by recording sound waves resulting from heart contractions and dilatations. It is an objective, in-depth and detailed listening of the heart. It is used mainly in obstetric practice, since auscultation of the fetal heart often does not reveal abnormalities in the heart rhythm and tone characteristics.…


Cardiotocography (CTG) is a simultaneous recording of fetal cardiac activity and uterine contractions in the dynamics, carried out using phonocardiography and Dopplerometry. A cardiotocogram consists of two graphs – a tachogram (fetal heart rate on a timeline) and a hysterogram (intensity of uterine contractions in dynamics). Based on cardiotocography data, it is possible to judge…

Dopplerography of Uteroplacental Blood Flow

Dopplerography of uteroplacental blood flow – registration of transplacental hemodynamics based on the Doppler effect. It is used for early diagnosis of pregnancy pathologies manifested by circulatory disorders in the “mother-placenta-fetus” system. Doppler ultrasound allows you to get a graphic image of the dynamics of blood flow through the vessels of the uterus and placenta.…

3D and 4D Ultrasound During Pregnancy

3D/4D ultrasound is a high-tech modern study that allows using ultrasound to obtain a detailed image of the fetus in three projections. 4D ultrasound is a more complex technique that allows you to additionally examine the fetus in motion. With the help of volumetric ultrasound, it is possible to diagnose intrauterine malformations: defects in the…

Third Trimester Screening

Third trimester screening is a complex of studies conducted on a planned basis from 30 to 34 weeks of gestation and visualizing the fetus, its internal organs, placenta, umbilical cord, uterus and amniotic fluid. It allows to diagnose incorrect presentation of the unborn child, pathologies of organ development, umbilical cord entanglement of the fetal neck,…

Second Trimester Screening Test

Second trimester screening test is a planned study that is performed at a period of 20-22 weeks, displays the structure and position of the placenta, umbilical cord, cervix, fetal size, structure and functioning of its internal organs. It allows you to diagnose the risk of termination of pregnancy, developmental delay and anatomical abnormalities of the…

First Trimester Screening

First trimester screening is a prenatal study that is performed from 11 to 14 weeks of gestation, visualizes the uterus, ovaries, fallopian tubes, corpus luteum, chorion, yolk sac, amniotic fluid and embryo. It allows you to diagnose the threat of spontaneous abortion, bladder drift, gross fetal pathologies, chromosomal diseases. It is indicated for single and…