What Is An Anomaly Scan?
An anomaly scan is an ultrasound scan taken around 20weeks of your gestation. This scan gives detailed information on possible structural abnormalities in your baby’s organs, the amniotic fluid level and the placental position.
An anomaly scan is the first indicator of possible abnormalities during pregnancy and is also called a mid-pregnancy ultrasound scan.
Detailed information on all these is to be discussed in the later sections of this page.
During an anomaly scan procedure, special attention is given to the anatomy of the skull, brain structure, face, two eye orbits with lens, nose, lips, chin, heart structure, lungs, stomach, two kidneys, intestines, bladders, segments of limbs, hands and toes.
A baby’s ears and the number of fingers and toes are examined only if there are any abnormalities with the other mentioned parts. In addition, this is also examined if you have a genetic disorder in your family
Best Anomaly Scan Centre in Chennai
Chennai Women’s Clinic at T.Nagar is the top choice for Anomaly Scan in Chennai by many moms-to-be. Getting your anomaly scan at Chennai Women’s Clinic means you can entrust your baby’s welfare in the hands of an award-winning Obstetrician and Gynecologist in the city, Dr Deepthi Jammi.
An anomaly scan is the first indicator of possible abnormalities during pregnancy and is also called a mid-pregnancy ultrasound scan.
Detailed information on all these is to be discussed in the later sections of this page.
During an anomaly scan procedure, special attention is given to the anatomy of the skull, brain structure, face, two eye orbits with lens, nose, lips, chin, heart structure, lungs, stomach, two kidneys, intestines, bladders, segments of limbs, hands and toes.
A baby’s ears and the number of fingers and toes are examined only if there are any abnormalities with the other mentioned parts. In addition, this is also examined if you have a genetic disorder in your family
When Will The Anomaly Scan Procedure Be Done?
Will The Anomaly Scan Provide 100% Confirmation Of The Structural Development?
What If There Are Signs Of A Problem In An Anomaly Scan?
How Can Patients Prepare For An Anomaly Scan?
What does your Fetal Medicine specialist examine during an anomaly scan?
The ultrasound waves help with a black and white 2-D image of your baby. This helps your fetal specialist carefully examine all the vital organs and take the measurements.
These are some of the examinations done,
- Abnormalities in the head/skull. At this stage, any abnormality in the brain development is also visible, along with any fluid accumulation.
- Associated with the brain abnormality can be a spinal cord defect. The baby's spine is examined both along its length and cross-section to ensure that all the bones align and that the skin covers the spine at the back.
- The baby’s face is checked for “cleft lip”. This is to diagnose any discontinuity between the nose and the baby's lips. But this is a challenging factor to identify since cleft palates are found times deep inside the baby's mouth.
- Any minor or major cardiac issues will be diagnosed. The top two chambers (atria) and the bottom two chambers (ventricles) should be equal in size. The valves should open and close with each heartbeat. The specialist will also examine the major veins and arteries which carry blood to and from the heart.
- The diaphragm and abdominal walls are examined for any hole or a rift. It is ensured if the abdominal wall covers all the internal organs at the front and checks the placenta, umbilical cord, and amniotic fluid.
- The stomach is examined to check if the amniotic fluid swallowed by the baby remains in the stomach.
- Your fetal specialist will check if both kidneys are present and if urine flows freely into the bladder. If the baby's bladder is empty, it should fill up during the period of the scan itself.
- Proper structuring of the bones will be checked along with the flexibility of arms, legs, hands, and feet.
- Once the body anatomy is studied, the amniotic fluid level surrounding the baby is checked.
- If the fluid level is reported normal, the placenta location is visualized. The placenta will be described as low if it reaches down to or covers the mouth of the uterus (the cervix). If the placenta lies low in the uterus, the patient will have another scan in the third trimester to check its position. By then, the placenta is likely to have been moved away from the cervix.
- It is possible to count the three blood vessels (two arteries and a single vein) in the umbilical cord, but it is not a routine procedure.
Will the baby's weight be included in the Anomaly Scan Report Details?
In addition to the above details, your anomaly scan report details three other measurements done to gauge the baby’s growth and weight:
- Head circumference (HC)
- Abdominal circumference (AC)
- Thighbone (femur) (FL)
The measurements taken during the anomaly scan should match upto what’s expected for the baby, depending on when the due date is.
Abnormal conditions are extremely serious, which may mean that a baby can’t survive. Or they may be treatable conditions, once the baby is born. If the condition is treatable, the fetal medicine specialist will collaborate with the obstetrician to enable adequate care once the child is born.
Fetal parts not mentioned under the ISUOG guidelines are not evaluated in an anomaly scan.
Can Down syndrome or chromosomal abnormalities be identified in the anomaly scan?
Only an amniocentesis test (testing the fluid surrounding the baby for its chromosomes) done during the first trimester can diagnose Down’s syndrome perfectly. In comparison, the ultrasound anomaly scan detects just 30% to 50% of cases of Down syndrome.
Sometimes babies with chromosomal abnormalities have signs called ultrasound markers. These include thick skin behind the neck (nuchal fold), absent nasal bone, mild fluid within the brain’s ventricles, an aberrant subclavian artery in the neck, occasionally short arms or legs. It is important to note that many normal babies also show these signs. The only way to accurately exclude or diagnose a chromosomal problem is to have an amniocentesis test.
Limitations of the anomaly scan
- Though the anomaly scan detects the abnormalities, your doctor cannot identify the reason behind malformation. In such cases, either a repeat test or genital counseling is recommended.
- Certain abnormalities like major cardiac issues, bowel obstructions, congenital diaphragmatic, hernia, hydrocephalus, microcephaly, club foot, kidney or intestinal obstruction may evolve during the later phase of pregnancy. The evolving variations cannot be diagnosed in an anomaly scan. Your fetal expert may recommend a repeat scan between 24 and 25 weeks of gestation in such situations.
- Some findings may not be anomalies but require scan follow-ups, biochemical testing or invasive testing. Some findings may be transient and may change with time
- Specialized Fetal Echo (heart study) or extended neurosonography (brain study) will be done if the referred doctor prescribes the same. Even if the brain may look normal on ultrasound examination, its function cannot be evaluated.
- Some anomalies like soft tissue fusion of fingers/toes, absence of anal opening or absence of auditory opening may not be recognizable by ultrasonography.
- Cleft lip found deep inside the mouth is a very challenging factor to be diagnosed with an ultrasound scan.
- Other factors such as the patient’s build, scars from a previous operation and the way the baby is positioned may limit the diagnostic ability of this test.
- Several factors like gestational age at which scan is done, the fetal position at the time of the scan, maternal body habitus, liquor volume, and shadows from fetal parts may restrict/limit the visibility of this scan.
- Ultrasound markers have only 50 to 70% capability to diagnose chromosomal anomalies. Consequently, invasive procedures for identifying Down's syndrome may be the best option. Your fetal expert can advise you on these procedures.
- Multiple gestations (twin/triplet pregnancies etc.) may cause difficulties in ultrasound examination due to fetal position and overlap.
- Even specialized fetal echocardiography (heart study) cannot pick certain cardiac anomalies such as Secundum ASD, small VSD, PDA, etc. A heart hole lesser than 5mm is also hard to diagnose in an anomaly scan.
- Obesity is a special challenge for ultrasonography. The fat in the mother’s abdominal wall absorbs the ultrasound energy, thus degrading the images and making the diagnosis very difficult.
- 3D/4D ultrasound is used only to assess certain abnormalities and is not a routine.
- The study of the genital organs is prohibited under the PC & PNDT Act. Hence detection of abnormalities of genital organs is not feasible.
Frequently Asked Questions
An anomaly scan is usually done between 18 and 22weeks of gestation. A fetal structure abnormality scan done anytime before this period shows only 22% accuracy.
You can take the anomaly scan during any time of the day without fasting or getting the bladder full. With the help of an ultrasound probe, your sonographer will be able to view a black and white 2-D image of your baby on the screen. Your baby’s essential body anatomy, placental position, and amniotic fluid levels are checked with the ultrasound waves.
The total scan procedure approximately takes about 30minutes to complete. If additional tests are required, this might extend briefly.
No. Anomaly scans are not painful.
Chennai Women’s Clinic being one of the best places for anomaly scan in Chennai gives the assurance of taking one step further in providing the most comfortable, safe, and clean scanning experience.
We are quite fast (10 – 15minutes approximately) in delivering your report. Your reports are generated parallelly when your scan is done. We make sure all your photo reports are laminated for you to treasure them for a lifetime