Fetal Anatomic Survey During Pregnancy
An anatomy scan is an ultrasound examination using sound waves to create an image of the fetus in the uterus. Its purpose is to assess the fetal organs and body systems, ensuring they are developing as expected and screening for anomalies.
As part of routine prenatal follow-up, it is now possible to undergo three anatomic surveys at different stages of pregnancy.
This scan can be performed using either a transvaginal or transabdominal method, depending on the pregnancy stage. Generally, the procedure is painless, though a vaginal ultrasound may cause slight discomfort; therefore, returning to your routine is possible immediately after the scan. However, if a second opinion is required, you may have to wait.
It is important to note
It is important to note
An anatomy scan cannot identify all potential pathological issues and anomalies, and a normal finding is not an absolute guarantee of the fetus's health.
-
1Early anatomic survey
As early as the first weeks of pregnancy, most of the fetal body systems are formed. The first anatomy scan is intended to examine these systems.
The goals of the examination:
- Scanning the fetal anatomic structure and the integrity of the various body systems according to the gestational age. It is important to note that at this stage, certain organs have not yet fully developed and can only be evaluated during the late scan.
- Identifying fetal anomalies that may indicate genetic syndromes. Please note that this examination does not diagnose genetic syndromes; however, it can assist in identifying findings suggestive of such syndromes. In the event of such findings, the woman will be referred for genetic counseling to discuss the possibility of undergoing amniocentesis.
- Identifying the location of the placenta.
Timing: Between week 14 to the end of week 16 of pregnancy.
The procedure: The scan is typically performed using a transvaginal ultrasound, while the woman lies on a gynecological exam table. The physician will cover the vaginal probe with a disposable sheath and apply ultrasound gel for lubrication. The probe is then gently inserted into the vagina to perform the scan. The examination takes place in a darkened room, so you can view the images together. In some cases, the scan may need to be complemented transabdominally (an abdominal ultrasound).
-
2Late anatomic survey
The second anatomy scan is also intended for identifying fetal anomalies or structural deformations. The scan, performed during the second pregnancy trimester, may be focusing on a specific organ, where an anomaly is suspected, or on a specific clinical issue that has to be monitored.
The goals of the examination:
- A thorough assessment of all the fetal organs from all angles, with particular focus on fetal biometry, including the Biparietal Diameter (BPD) which measures the width of the skull – along with head and abdominal circumferences, and femur length (FL).
- Visualization of fetal organs, and where necessary, measuring their size, and ensuring they fall within the norm.
- Imaging of the fetal face, heart structure, and extremities.
- Correlating scan findings with gestational age.
- Fetal weight estimation.
- Identifying placenta's location.
- Assessment of amniotic fluid volume.
- In multiple pregnancies: evaluating the number and location of gestational sacs, as well as determining chorionicity and amnionicity (the status of placental membranes).
Timing: From week 20 to the end of week 24 of pregnancy.
The procedure: The scan is typically performed using a transabdominal ultrasound. The physician will apply a clear ultrasound gel on the abdomen for lubrication and then move the probe over the abdomen to perform the scan. The examination takes place in a darkened room, so you can view the images together. Most detailed scans combine 2D and 3D ultrasound to produce very high-resolution images of the fetus; occasionally, this includes the fetus in motion, 4D imaging.
-
3Third anatomic survey
In the third scan, all fetal organs and systems are examined; however, the focus is now particularly on fetal development and growth appropriate for the advanced stage of pregnancy. Occasionally, during the third scan, abnormal findings will be identified. Some of these will be treatable even at this late stage of pregnancy. In certain cases, it may be necessary to consider, in consultation with various medical specialists, an early delivery, and to prepare in advance for the newborn's immediate care following birth.
The goals of the examination:
- Examining fetal organs and their size, focusing on the brain, skeleton, heart, kidneys, digestive system, and urinary tract.
- Identifying findings that can be detected at this stage of pregnancy, for example: skeletal dysplasia (dwarfism), ventriculomegaly (enlarged brain ventricles), polyhydramnios (excess amniotic fluid), placental issues, and more.
- Placenta location and functioning.
- Amniotic fluid volume.
- Fetal size and weight estimation.
Timing: From week 30 to the end of week 32 of pregnancy.
The procedure: Similar to the late anatomy scan.
It is important to note
It is important to note
Not all women undergo three fetal anatomy scans during pregnancy; Most undergo one or two scans according to medical recommendations. The third is performed as needed or by personal choice. This is only general information, and recommendations vary from woman to woman; therefore, it is important to consult your primary care physician.