When Should a Detailed Ultrasound Be Performed and What Problems Can It Detect?

Detailed ultrasonography is an important ultrasound examination in which the baby’s organs and systems are evaluated in detail during pregnancy. It is generally performed between 18 and 22 weeks of pregnancy. During this period, many anatomical structures, including the baby’s brain, face, heart, spine, chest, abdominal organs, kidneys, urinary tract, arms and legs, can be examined in detail. The placenta, amniotic fluid and other features of the pregnancy are also evaluated.

The purpose of detailed ultrasonography is not merely to obtain images of the baby or determine the baby’s sex. The main aim is to assess the baby’s development and identify structural abnormalities that may be detected during pregnancy as early as possible.

However, the absence of a problem on detailed ultrasonography does not guarantee that the baby has no health or genetic condition. Some diseases may not produce ultrasound findings, while some abnormalities may become apparent only at later stages of pregnancy.

A detailed ultrasound is a comprehensive ultrasonographic examination in which the baby’s anatomical structures are evaluated systematically. It may also be described using terms such as “detailed ultrasound,” “level II ultrasound,” or “fetal anomaly scan.”

The examination does not assess only the baby’s size. Many structures, including the head and brain, face, spine, heart and great vessels, lungs, abdominal wall, stomach, kidneys, bladder, arms and legs, are evaluated in specific ultrasonographic planes.

In addition, the baby’s growth, placental location, amount of amniotic fluid, umbilical cord and other pregnancy-related structures are examined.

The aim is to evaluate the baby’s anatomical development as comprehensively as possible at this stage of pregnancy.

The most commonly preferred period for a detailed ultrasound is between 18 and 22 weeks of pregnancy.

By these weeks, most of the baby’s organs have developed sufficiently to be evaluated in detail by ultrasonography. At the same time, the baby’s size and the imaging environment provided by the amniotic fluid allow many anatomical structures to be examined.

However, there is no single, fixed week that applies to every pregnancy. Depending on the characteristics of the pregnancy, a previously detected finding or technical reasons, the assessment may be performed earlier or later.

International guidelines may define a period of approximately 18–24 weeks of pregnancy for routine mid-trimester fetal ultrasound examination.

In the early stages of pregnancy, many of the baby’s organs are still too small for detailed assessment, and in particular some intracranial structures have not yet completed their development. As pregnancy progresses, the anatomical structures of the brain, heart, spine, kidneys and other organs become more suitable for detailed ultrasonographic evaluation.

The 18–22-week period is important in this respect.

Nevertheless, a normal first-trimester ultrasound does not mean that a detailed ultrasound is unnecessary in the second trimester. Some structural abnormalities may not be visible early in pregnancy or may become apparent only as pregnancy progresses.

Similarly, a normal detailed ultrasound in the second trimester does not mean that no problem can arise later in pregnancy.

During a detailed ultrasound, the baby’s anatomy is evaluated according to a systematic approach.

The shape and integrity of the baby’s skull, the main anatomical structures of the brain and certain spaces within the brain are evaluated.

Some serious abnormalities of brain development, enlargement of the ventricles, development of the cerebellum, midline structures, or certain conditions affecting the skull may be identified during this examination.

The baby’s facial profile, lips and certain facial structures are evaluated.

Some facial abnormalities, particularly cleft lip, may be visible on ultrasonography. However, evaluation of the face can be affected by the baby’s position, and it is not possible to detect every facial abnormality by ultrasonography.

The heart is an important part of the detailed ultrasound examination.

The position and size of the heart, the four-chamber view, the great vessels arising from the heart and the heart rhythm are evaluated. This examination may help detect some important congenital heart abnormalities.

However, a normal-appearing heart on detailed ultrasound does not exclude all heart diseases. If there is a suspicious finding, family history or certain risk factors, a more detailed examination called fetal echocardiography may be required.

The baby’s spine is evaluated in different planes to examine the alignment of the vertebrae and the integrity of the spine.

Some spinal abnormalities, such as spina bifida, may be detected during detailed ultrasound.

The baby’s chest, the appearance of the lungs and the diaphragm are evaluated.

Some space-occupying masses in the chest, lesions affecting lung development, or abnormalities such as congenital diaphragmatic hernia may be visible on ultrasonography.

The integrity of the baby’s abdominal wall, the appearance of the stomach and some of the organs within the abdomen are evaluated.

Abdominal wall abnormalities such as gastroschisis and omphalocele are among the structural problems that may be detected during this period.

The presence, location and appearance of both kidneys, as well as the filling and emptying of the bladder, are evaluated.

Kidney enlargement, certain kidney abnormalities, or findings suggestive of urinary tract obstruction may be identified during detailed ultrasound.

For example, a markedly enlarged fetal bladder accompanied by urinary tract dilatation or reduced amniotic fluid may require investigation for conditions such as lower urinary tract obstruction (LUTO).

The baby’s arms and legs, long bones, hands and feet are evaluated as far as possible.

The length and appearance of the bones may provide information about certain skeletal system abnormalities.

Yes. A detailed ultrasound is not an assessment limited to the baby’s organs.

The location of the placenta within the uterus is evaluated. Conditions in which the placenta is close to or covers the cervix may be identified. The site where the umbilical cord inserts into the placenta and assessment of placental invasion into the uterine wall are also examined during the evaluation.

The amount of amniotic fluid is also assessed. A lower or higher than normal amount of amniotic fluid may sometimes be associated with various maternal, fetal or placental conditions.

Certain features of the umbilical cord and, depending on the pregnancy, blood flow assessments may also be included.

A detailed ultrasound may help detect many structural abnormalities. These may include:

• Certain abnormalities of the brain and skull,
• Spinal abnormalities such as spina bifida,
• Certain congenital heart abnormalities,
• Certain facial abnormalities such as cleft lip,
• Diaphragmatic hernia,
• Certain lung abnormalities,
• Abdominal wall abnormalities,
• Certain abnormalities of the kidneys and urinary tract,
• Certain skeletal system abnormalities,
• Certain conditions affecting the baby’s growth

may be among them.

However, not every abnormality has the same detectability on ultrasonography. Some structural problems are easier to see on ultrasound, while others may be very small, may not yet have developed, or may not be visible because of the baby’s position.

Therefore, although detailed ultrasound is a diagnostic and assessment method, it is not a test that can show all diseases in the baby.

Detailed ultrasound is not a diagnostic test for Down syndrome.

In some chromosomal abnormalities, structural problems in the baby’s anatomy or certain findings described as ultrasound “markers” may be seen. However, the presence of these findings does not necessarily mean that the baby has a chromosomal disorder, and a completely normal ultrasound does not definitively exclude chromosomal disorders.

Screening tests such as NIPT and diagnostic tests such as amniocentesis or chorionic villus sampling (CVS) serve different purposes from detailed ultrasound in the assessment of chromosomal disorders.

Therefore, when an ultrasound finding suspicious for a chromosomal problem is detected, current screening results, maternal age, family history and other clinical information may be evaluated together, and genetic counseling or further testing may be considered.

A normal detailed ultrasound is an important and positive finding, but it does not guarantee that the baby is completely healthy.

Ultrasonography primarily evaluates the baby’s anatomical structure. Some genetic diseases, metabolic diseases, hearing or vision problems, and certain diseases that may appear after birth may not produce any ultrasonographic finding.

In addition, some structural abnormalities may become apparent later in pregnancy.

The diagnostic capability of ultrasonography may also vary depending on the type of abnormality, gestational age, the baby’s position, the mother’s body habitus, amniotic fluid and imaging conditions.

Therefore, the statement “the detailed ultrasound is normal” means that the anatomical structures that could be evaluated during the examination appeared normal on ultrasonography; it does not mean that all diseases have been excluded.

Detection of a finding on detailed ultrasound does not always mean that the baby has a serious disease.

Some findings may be temporary or may require only follow-up. In other cases, the detected finding may need to be evaluated in greater detail.

Depending on the findings, the following may be considered:

• Repeating the detailed ultrasound,
• Fetal echocardiography,
• Fetal MRI,
• Evaluation with NIPT or other genetic screening methods,
• Diagnostic genetic tests such as amniocentesis,
• Serial ultrasound follow-up

may be considered.

The important question is not only “What was seen on ultrasound?” The meaning of the finding for the baby’s development, whether it is associated with other abnormalities and whether it may alter the course of the pregnancy should also be evaluated.

Some fetal abnormalities are only monitored throughout pregnancy and the necessary treatment is performed after birth. In selected conditions, depending on the baby’s condition, fetal therapy or fetal intervention options in the womb may be considered.

No.

The term “detailed ultrasound” describes the scope of the examination and the detailed assessment of the baby’s anatomy. Three- or four-dimensional ultrasound refers to the way the image is obtained and displayed.

Two-dimensional ultrasonography forms the basis of detailed fetal anatomical assessment. When considered necessary, 3D or 4D imaging may provide additional information.

Therefore, merely obtaining three- or four-dimensional images of the baby does not mean that a detailed ultrasound has been performed.

Second-trimester fetal anatomical ultrasound assessment is not only for high-risk pregnancies.

Low-risk results from early pregnancy screening or genetic screening tests do not eliminate the need for anatomical assessment of the baby. Structural abnormalities can occur even in the absence of a chromosomal problem.

However, fetal assessment may become particularly important in situations such as a previous pregnancy affected by an anomaly, a family history of genetic disease or congenital anomaly, exposure to certain medications or infections during pregnancy, multiple pregnancy, or a suspicious finding on previous examinations.

The duration of the examination may vary depending on the baby’s position, gestational age, imaging conditions and whether additional assessment is required.

If the baby is not in a suitable position for visualizing certain anatomical structures, the examination may take longer. Sometimes the mother may need to move for a while or the assessment may need to be completed later.

If a structure cannot be adequately visualized during the first examination, this does not necessarily mean that there is a problem with that structure. A follow-up ultrasound may be planned when the examination cannot be completed because of technical conditions.

It is generally performed between 18 and 22 weeks of pregnancy. However, timing may vary according to the characteristics of the pregnancy, previously detected findings and imaging conditions.

During a detailed ultrasound, the baby’s anatomical structures are comprehensively evaluated according to a defined systematic approach. The aim is not merely to assess the baby’s growth or see the heartbeat, but to examine the anatomy of the organs and systems in detail.

No. Detailed ultrasound is not a diagnostic test for Down syndrome. Some ultrasound findings may suggest an increased risk of chromosomal disease, but screening and, when necessary, diagnostic genetic tests are used for definitive assessment.

The necessary tests are determined according to the characteristics of the pregnancy, previous screening results, maternal and family history, and clinical risks. A normal detailed ultrasound does not replace other screening or diagnostic tests.

Depending on the finding, additional examinations such as a more detailed ultrasound, fetal echocardiography, fetal MRI, genetic evaluation or amniocentesis may be required. In some cases, ultrasound follow-up at specific intervals may be sufficient.

No. The main purpose of detailed ultrasound is to evaluate fetal anatomy systematically, and two-dimensional ultrasonography forms its basis. 3D or 4D ultrasound may be used as a complementary method when necessary.

This content has been prepared for general informational purposes. The timing and scope of detailed ultrasound should be evaluated individually by the physician, taking into account the characteristics of the pregnancy, the clinical condition of the mother and baby, and the results of previous examinations.