FAQs
Obstetric Ultrasound
- Can I empty my bladder before the scan?
- Yes if you are less than 7 weeks pregnant. In the early gestation period the Sonographer will have to perform a transvaginal scan to be able to assess the pregnancy. If you are more than 7 weeks gestation then we ask our ladies not to empty. The bladder is used as an acoustic window to improve the image quality and it also improves the position of the womb and the baby.
- Can my baby feel the ultrasound?
- No, the ultrasound scan is performed with the help of high frequency sound waves, therefore if you can't hear or feel it, the baby can't.
- Is there a limit to the amount of ultrasound scans I can have during my pregnancy?
- We try to encourage our patients not to have scans just to see the baby. We limit the scans to those of medical value, as it is not clear as of yet how many scans is safe, because there is no data to suggest that a certain number is allowed and the rest there after will do harm.
- Can I bring my partner or family?
- Yes it is always nice to share the experience and we encourage our patients to bring someone along. It is very helpful when we discover a problem on scan and then the patient will have someone to support her.
- At what age can I find out what sex my baby is?
- The best time is at your 20 week anomaly scan, allowing that the baby is in a good position.
- What is nuchal translucency?
This is a collection of fluid under the skin at the back of the baby's neck at 11 – 13 weeks 6days that can be measured using ultrasound. All babies have some fluid, but in many babies with Down's syndrome, the nuchal translucency (NT) is increased.
An NT scan is a method of assessing whether your baby is likely to have Down's syndrome. It's a screening test. A screening test can only estimate the risk of your baby having Down's syndrome, as opposed to a diagnostic test, such as CVS or Amniocentesis, which will give you a definite diagnosis (but also carries a small risk of miscarriage).
The NT scan can't tell for certain if your baby is affected. However, it can help you decide whether or not to have a diagnostic test.
- When can I have the test?
- NT scan are performed from 11 to 13 weeks 6days of pregnancy. Before 11 weeks the scan is technically difficult because the baby is so small, after 14 weeks, excess fluid may be absorbed by the baby's developing lymphatic system.
- How is the test done?
The first part of the Combined test involves an ultrasound scan. The scan is usually done through your tummy, but depending on the position of your womb and your baby, sometimes it is necessary to perform a vaginal scan, which will give better views. There is no risk to you or your baby and it should not be too uncomfortable.
To accurately date your pregnancy the Sonographer will measure your baby from the top of its head to the bottom of the spine, also known as the crown-rump-length (CRL). The Sonographer will then measure the width of the NT.
The second part of the test involves a blood sample taken from you on the day after the scan.
- What is a normal measurement?
An NT measurement up to 2mm is normal at 11weeks, and up to 2.8mm by 13weeks 6days.This is because the NT normally grows in proportion to the growth of the baby.
Normal nuchal translucency
Borderline nuchal translucency
Very abnormal nuchal translucency
If the NT is increased, it does not mean there is definitely a problem. Some normal babies have increased fluid, too.
Image two shows a baby with a NT of 2.9mm, which is just outside the normal range. Though the risk will be higher than the baby's in the first image, 9 out of 10 babies with a measurement between 2.5mm and 3.5mm will be completely normal.
As the NT increases, so does the risk. The baby in image 3 has a NT of 6mm and will be at very high risk for Down's syndrome, as well as other chromosomal and genetic syndromes and heart problems.
- How is the risk calculated?
- Every woman has a risk of giving birth to a baby with Down's syndrome, and this risk increases with age. A risk will be calculated for your baby using your age, the NT measurement, the result of the blood test and your background history.
- What is Renal Pelvis Dilatation?
Renal Pelvis Dilation
Urine that is produced by the baby's kidneys collects in the middle before going down tubes called ureters into the bladder. The build-up of fluid is usually due to a slight obstruction in the flow of the urine. The tubes get bigger as the baby grows and will allow urine to flow more easily. When the renal pelvis appears slightly bigger than usual during the scan, i.e. more than 5mm but less than 10mm, it is called mild renal pelvis dilatation.( see image of mild renal pelvic dilatation)
- Is this finding common?
- This finding is present in about 1% of pregnancies, i.e. one in every 100 women.
- Are the kidneys normal?
- Apart from the mild dilatation seen on the scan today, all the other structures in the baby appear normal. In the vast majority of cases, this is a temporary finding and causes no problem to the baby. In a very small percentage of cases (about 4%) there is a problem with the kidneys that may require some treatment after birth. To assess this we will suggest an appointment for a repeat scan at 30 weeks with a Fetal Medicine Consultant to see if the dilatation is still present or has increased.
- Do I have to worry that anything else is wrong?
- Several studies have shown that there is a weak association between mild renal pelvic dilatation and Down's Syndrome. It is important to realize that the association is weak and the best way of assessing the risk for your baby is to consider your age or other screening tests for Down's Syndrome you may have had performed earlier in your pregnancy. If your previous risk was low, and the scan shows no other features associated with Down's Syndrome, the finding of mild renal pelvic dilatation alone does not significantly increase the risk.
- What happens if the dilatation is still present at my 30 week scan?
- If the dilatation has disappeared there is no need for further tests. If the dilatation is still present but remains mild, there is no need for a further scan. However your baby should see a Paediatrician when he or she is a few days old to follow up the dilatation of the renal pelvis, as some babies are at an increased risk of urine infection. If the dilatation of the renal pelvis is greater than 10mm then an appointment with a Fetal Medicine Consultant will be suggested.
- What if I am still worried about Down's Syndrome?
- An ultrasound scan will pick up about 50% cases. Blood tests earlier in pregnancy are much better, but the only way to be certain is to have an Amniocentesis.
- What are Echogenic foci ("golf balls")?
"Golf balls" appears as small white balls attached to a muscle in the heart, most commonly in the left ventricle. Though occasionally associated with heart defects or chromosomal abnormalities, they are common and most are probably a variation of normal.
Image 1 and 2 demonstrate a small echogenic foci in the left ventricle
- Is this finding common?
- This finding is present in about 4% of pregnancies, i.e. four in every 100 women.
- Is the heart normal?
- Apart from the echogenic foci in the ventricles the scan today shows that all the other structures in the baby's heart appear normal. In the vast majority of cases, this causes no problem to the baby.
- Do I have to worry that anything else is wrong?
- Several studies have shown that there is a weak association between echogenic foci and Down's Syndrome. It is important to realize that the association is weak and the best way of assessing the risk for your baby is to consider your age or other screening tests for Down's Syndrome you may have had performed earlier in your pregnancy. If your previous risk was low, and the scan shows no other features associated with Down's Syndrome, the finding of golf balls alone does not significantly increase the risk.
- What if I am still worried about Down's Syndrome?
- An ultrasound scan will pick up about 50% of cases. Blood tests earlier in pregnancy are much better, but the only way to be certain is to have an Amniocentesis.
- What are Choroid plexus cysts?
Choroid plexus cysts are just a collection of fluid in the part of the baby's brain that makes the fluid that cushions the brain and spinal cord. The "cyst" is just a small build-up of fluid as it moves through the connecting tubes. As the baby grows the tubes get bigger and the fluid moves on. CPC's are almost always gone by 24 weeks and do no harm to the baby's brain.
CPC's look like black spots in the hemispheres of the brain.
Babies with Edward's syndrome (Trisomy 18) are found to have CPC's. However research has shown that babies with Edward's syndrome also have other abnormalities, such as strawberry-shaped head (see image below), overlapping fingers and abnormal feet, heart, kidney or abdominal problems.
It is known that 1% of babies have one or more CPC's in early pregnancy (see image 2 below). In the absence of other markers (isolated CPC's) they are insignificant and Sonographers in many hospitals don't even mention them any more.
Choroid plexus cyst in a baby with Edward's syndrome
Choroid plexus cysts in a normal baby
A follow-up scan at 30 weeks will be suggested by the Sonographer if the CPC's measures equal to or more than 5mm in AP diameter. This is not to assess the resolution of the CPC's, but to assess the baby's growth, as babies with Edward's syndrome demonstrates growth restriction and will be small for gestational age.- Is this finding common?
- This finding is present in about 1% of pregnancies, i.e. one in every 100 women.
