The Anomaly Scan Explained: What the 18–20 Week Ultrasound Checks
The Anomaly Scan Explained: What the 18–20 Week Ultrasound Checks
An anomaly scan is a detailed ultrasound performed during the middle of pregnancy to examine the baby's development. It is usually offered between 18 and 22 weeks, depending on local clinical guidance and the pregnancy care plan.
The scan looks at the baby's major organs and body structures, including the brain, spine, heart, abdomen and limbs. It also checks the placenta and amniotic fluid. It can identify some structural conditions, although no ultrasound can detect every possible problem.
Why Is the Scan Done Around 18–20 Weeks?
By this stage, many of the baby's structures can be examined in greater detail using ultrasound. The scan gives the healthcare team an opportunity to assess development and check for certain structural abnormalities.
Your doctor may recommend a scan at a slightly different time depending on your pregnancy, local guidelines and the availability of appointments.
What Does the Anomaly Scan Check?
During the scan, the sonographer examines several parts of the baby's body, including:
-
Brain and skull: The size and visible structures of the brain and skull are assessed.
-
Spine: The spine is examined for visible structural abnormalities.
-
Heart: The heart's position, chambers and selected views of its structure are checked.
-
Face: The facial structures, including the upper lip, may be examined.
-
Abdomen and internal organs: The stomach, kidneys, bladder and abdominal wall are assessed.
-
Arms, legs, hands and feet: The visible development of the limbs is checked.
-
Placenta and amniotic fluid: The placenta's position and the amount of fluid around the baby are assessed.
-
Growth: Measurements are taken to assess the baby's size and development.
The exact structures assessed may vary depending on the scan protocol and how clearly the baby can be seen.
How Long Does an Anomaly Scan Take?
A detailed anomaly scan often takes around 30–45 minutes, although the time can vary. The sonographer needs to obtain clear views of several structures, and the baby's position can affect how quickly this is possible.
If the baby is lying in a position that makes certain views difficult to obtain, you may be asked to walk for a short time or return for another scan. A repeat scan does not automatically mean that a problem has been found; sometimes the team simply needs clearer images.
What Happens If the Scan Finds Something Unexpected?
If the scan identifies a finding that needs further assessment, your doctor will explain what was seen and discuss the next steps. Depending on the finding, this may involve a repeat ultrasound, a more detailed scan or referral to a specialist.
Sometimes the scan cannot provide a complete view of every structure. In that situation, another appointment may be recommended to finish the assessment.
It is important to remember that an anomaly scan can identify some structural concerns, but a normal result cannot guarantee that a baby has no health conditions. Your doctor can explain the findings in the context of your pregnancy.
Pregnancy Care at Vignesh Hospital & Guna Fertility Centre
Vignesh Hospital & Guna Fertility Centre in Lalgudi, Trichy, provides fertility, obstetrics and gynaecology services as part of its long-standing community healthcare work.
