|What Is An Anatomy Scan?
Also known as an anomaly scan or anatomic survey, an anatomy scan is the most extensive ultrasound exam carried out on the fetus during pregnancy. It is performed between weeks 18 and 22 and is the one most people are referring to when they talk about their routine pregnancy scan or their 20 week scan. The baby's gender can usually be reliably revealed in this scan (see, how accurate is a scan at predicting gender?). It is performed as an abdominal scan (a transvaginal scan, where a probe inserted into the vagina is only performed if there is a risk of premature birth). There has been some medical debate as to whether an anatomy test should be routinely performed, particularly in cases where a termination is not an option. Yet, studies consistently show that infant mortality rates are lower when it is performed. Additionally, pregnancy complications are reduced, particularly where placenta problems have been identified and corrected.
Benefits Of Anatomy Scan
Advance Warning System
If doctors discover a serious birth defect, the baby has a better chance of survival if the problem is detected before birth. This is because it allows the medical team to prepare for the birth and ensures the birth will take place at a hospital medically equipped to take care of the newborn. For example, if the baby has a heart defect, being born in a hospital staffed with pediatric cardiologists can mean the difference between life and death.
Treatments Before Birth
Most birth defects can only be treated once the baby is born. In some cases however, temporary interventions can be performed while the baby is still in the womb (in utero). For example, if the baby's bladder or kidneys are blocked, doctors can make a small hole in the uterus and insert a tiny surgical tool called a fetoscope. With the fetoscope, tubes or shunts can be placed in the bladder or kidneys to temporarily free up the area. Most in utero treatments are only temporary and further surgery will be required after birth.
Soft markers are non-definitive, subtle and usually harmless physical signs that your baby has Down syndrome. If they are found, you will be told that there is a high risk that your baby has Down's and you may be offered more invasive testing - namely an amniocentesis or chorionic villus sampling (CVS test).
What An Anatomy Scan Can Detect
||Percentage of cases detected
|Spina bifida (open spinal cord)
|Anencephaly (top of the head missing)
|Hydrocephalus (fluid in the brain)
|Major heart problems (congenital heart defects)
|Diaphragmatic hernia (defect in the muscle which separates the chest and the abdomen)
|Exomphalos/gastoschisis (defects of the abdomen)
|| 90 percent
|Major kidney problems (either missing or abnormal kidneys)
|| 85 percent
|Major limb abnormalities: (missing bones or very short limbs)
||About 40 percent
What Happens During The Scan?
An anatomy scan takes much longer than any other type of pregnancy scan - it usually lasts 40 minutes but can take longer if the baby is not cooperating by lying in the correct position. You may be asked to jiggle your belly or take a short walk to get junior to cooperate. During the procedure gel is smeared to the belly area to ensure good contact between the skin and transducer (the device that emits ultrasonic waves). The transducer is placed on the belly and is rolled back and forth while internal images can be seen on a monitor next to the technician. In earlier scans the sonographer (technician) only takes 8 or 12 images, with this scan 40 or 50 may be taken.
Images Taken During The Scan
Head and Brain
A cross section of the head is taken and with this measurements are taken just above the ears to get the circumference. Other brain structures will also be investigated. By looking at these scans many head problems can be ruled out including hydrocephalus (water on the brain).
A cross-sectional view of the spine is taken, this helps to identify spina bifida.
The baby's stomach, kidneys and bladder are examined for any blockages. The sonographer checks that all the organs are present and in the right position. The umbilical cord is checked, there should be 2 arteries and 1 vein going through it. The heart is evaluated - don't worry if the technician spends a lot of time on the heart area, it is one of the most difficult areas to evaluate so it may take time to get the right images. If the sonographer uses a color Doppler, you will see red and blue flashes of color on the monitor which represent your baby's blood flow. If a problem with the heart is detected you may be referred to a fetal cardiac specialist for a fetal echocardiogram.
Faces And Limbs
3D ultrasound imaging will be used to capture the baby's face. While it will give you very cute images, it will also help to detect cleft palate or cleft lip. Images are taken of the feet to rule out clubfoot. The sonographer may try to take pictures of the fingers but usually the fists are closed so this is difficult.
Your amniotic fluid levels and womb (uterus) will be looked at; as well as the cervix for signs of dilation which could indicate a preterm birth. The location of the placenta is noted. If the placenta is found to be blocking the cervix (which would make delivery difficult and is known as low-lying placenta or placenta previa) it will need to be closely monitored with follow up scans. If it is still low by week 36, a cesarean section will need to be performed. Fortunately in most cases, by the third trimester, it is no longer a concern.
At the end of your scan you will be given images of your baby and a detailed report on the findings. Read about pregnancy ultrasound photos and videos which you may be offered.
If My Scan Is Normal Does That Mean My Baby Is Healthy?
Most of the time, yes - however, it is not a guarantee. While the test can rule out many physical abnormalities it may miss subtle defects - particularly heart problems. It may also miss organ function and metabolism disorders, as well as other non-visible problems such as autism.
What Happens If My Scan Is Not Normal?
You will be told at the time of the scan if a problem is suspected. If there is concern, you will be asked back for further scanning and discussion with a fetal medical specialist (usually within 24 hours). Most problems that need repeat scanning are not serious - about 15 percent of women are investigated further.
How Much Do Anatomy Scans Cost?
Without insurance an anatomy scan costs between $270 and $360.
Related Questions and Answers
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Third trimester ultrasound scan
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