All about ultrasound

My baby album consists of a few grainy pictures of me being propped up, fed and generally manhandled by my older sisters. It’s not the case with my son, Michael. Before you even get to his Day 1 pictures in his photo album, there’s a string of ultrasound pics documenting his progression from tadpole, to alien, to a foetus that hiccupped, sucked his thumb and waved to his mommy (very advanced, Michael was…). Ultrasounds have taken the mystery, worry, surprise and, more importantly, medical uncertainty out of childbirth, but how do they work and what are they really looking for?

How do they work? High-frequency sound waves pass from the probe, which is handled by the doctor, or sonographer, into the uterus and are reflected back. A chilly water-soluble gel is used on the skin to ensure good contact. A computer interprets the reflected sound waves as two-dimensional black and white images on a screen for viewing and diagnosis.

What do they look for? Mostly, they are used to monitor the foetus, diagnose any potential malformations, assess the health of the placenta and take measurements to ensure the baby’s skeleton, brain, heart and organs are growing properly and appropriately for its gestational age.

However, there are a number of different scans, offered at different times of pregnancy, and it can get a little confusing for a mom-to-be. Doctors recommend that pregnant women get two crucial ultrasound scans done during a pregnancy, the nuchal scan and the foetal anomaly scan, both of which are covered by most medical aids.

The nuchal translucency scan
The nuchal translucency (NT) scan, usually performed between 11 and 13 weeks, is primarily used to measure the amount of fluid at the back of the baby’s neck and to confirm if it has a nasal bone. These simple measurements can pick up almost 90 per cent of babies with Down’s syndrome.
“If you’re not trained properly to perform this scan, you can only expect to pick up 50 per cent of foetuses with Down’s syndrome,” warns Dr Linnie Muller, foetal medicine specialist at Panorama Fetal Medicine Centre.
“If you are concerned about the skill of your obstetrician, you are better off having the old blood test at 16 weeks instead.”

WHAT WILL HAPPEN IF THE RESULTS ARE BAD?
The NT measurement, nasal bone, along with the results of a blood test performed at the same time, and your age, would be analysed together to assess the risk of your baby having Down’s syndrome. If the results suggest you are at an increased risk of having a baby with Down’s syndrome, a diagnostic test, such as an amniocentesis, might be recommended.

WHAT ELSE ARE THEY LOOKING FOR?
Your doctor will also measure your baby from her head to her buttocks to confirm how far along your pregnancy is and to determine a due date. The size of your baby is also checked to ensure she is growing properly.

WHAT WILL YOUR BABY LOOK LIKE?
Two-dimensional ultrasound is like looking at a single slice from a loaf of bread so you might not see the whole of the baby in one picture. However, you will be able to see a blurry nose, lips, body and limbs and you’ll see your baby moving and swallowing.

IS YOUR DOCTOR ACCREDITED?
Only a small number of South African doctors are accredited to perform the nuchal translucency scan. To check if your doctor is registered with Fetal Medicine Foundation, go to www.fetalmedicine.com. “If you are not sure if your doctor is accredited, ask if they have the software to generate the risk profile. If not, they are not accredited,” says Dr Ilse Erasmus, secretary of the South African Society for Ultrasound in Obstetrics and Gynaecology.

Ask your doctor to refer you or call SASUOG on 012-347-3344 for details of an accredited foetal medicine centre near you. The website www.sasuog.org.za will be uploading a comprehensive list for patients soon.

Routine scans

The foetal anomaly scan
This scan is performed at between 20 and 22 weeks and checks your baby’s organs and limbs in detail to look for abnormal growth, malformations and other potential problems. Your doctor will be looking for further markers for specific syndromes and measuring your baby’s legs, trunk, arms and head size. Shorter limbs can indicate skeletal problems, for example. The position of the placenta is also checked to ensure it is not blocking the birth canal and does not pose a risk during labour. The amount of amniotic fluid is also tested. Abnormal levels can indicate developmental malformations or kidney problems.

WHAT WILL HAPPEN IF THE RESULTS ARE BAD?
You will be counselled by a team of appropriate experts about what further tests should be done (eg amniocentesis, transvaginal scan or MRI scan of the baby’s head) and the implications of these. This could range from considering termination to preparing you emotionally for challenges the baby may face at birth or later in life.

WHAT ELSE ARE THEY LOOKING FOR?
Scans can also detect neural-tube defects (such as spina bifida), a cleft lip or palate and heart and other organ defects. The way the baby moves will also indicate potential problems.

WHAT WILL YOUR BABY LOOK LIKE?
The brain, spine, heart and other organs will all be clear. You’ll be able to count fingers and toes and confirm the sex of the baby if it is lying in a suitable position to get a peek.


Transvaginal or pelvic scan
While pregnancy is most often confirmed by a blood test, your doctor might offer you a scan as early as six weeks to confirm the baby’s heartbeat and check the gestational sac and yolk sac are normal and in the correct place (not a Fallopian tube). This is usually a pelvic scan.

The probe (a long, phallic-shaped instrument) is inserted into your vagina. It’s often used when an ectopic pregnancy (a pregnancy outside of the uterus) or molar pregnancy (a mass of tissue that mimics the symptoms of pregnancy) is suspected, when there has been bleeding (to check if the baby is alive) and later in pregnancy when the baby can’t be seen by a regular ultrasound or the mom is very overweight.

If the scan can detect an embryo but no heartbeat, a missed abortion (the medical term for when a foetus dies but remains in the uterus) is diagnosed. A repeat scan will be done seven to 10 days later to confirm this and you may be offered a D&C (a dilation and curettage removes remaining tissue from the uterus) if this is the case. Emergency laparoscopic surgery is required if an ectopic pregnancy is diagnosed.


The doppler scan
This is often performed by your doctor during your anomaly and growth scans. It doesn’t involve using a different probe; they simply switch the machine to this alternative function. It gives a black and white or colour image tracing the blood flow between the placenta and your baby.

It also assesses your risk of preeclampsia, a dangerous blood-pressure condition. Colour-flow mapping can also chart the flow of the foetus’s blood and pick up potential problems such as cardiac defects and conditions such as anaemia.

WHAT WILL HAPPEN IF THE RESULTS ARE BAD?
If a slower-than-normal heartbeat is detected between five and eight weeks, your risk of miscarriage is high. However, all women ovulate at different times, so a single scan is not cause to worry. A further scan a week or two later will be done to reassess things.


3d and 4d scans
These modern scans – often referred to as “picture scans” – make use of ultrasound differently. They take a series of images from different perspectives of the baby and the computer processes them as a multi-dimensional image. They can be done briefly in addition to the diagnostic 2D scans at your foetal anomaly scan or at a private clinic that specialises in only doing 3D picture scans. They are not diagnostic scans, but they do give you your first glimpse of what your baby will really look like.

Many moms and dads-to-be find the 3D/4D images an important part of the bonding process. “It makes the pregnancy so much more real,” says Dr Muller. “I still get surprised at their reaction when they see it – it’s the most beautiful thing.”

WHAT’S THE DIFFERENCE BETWEEN 3D AND 4D?
Depending on the weight of the mother and the position of the baby, a 3D scan gives a single still image of the foetus. However, if the baby moves the picture will be distorted. “4D scans can incorporate movement and we get brilliant images,” says sonographer Melanie Reyneke of Peek-a-Babe 4D Scan.

WHAT WILL YOUR BABY LOOK LIKE?
For the first time you will be able to see a lifelike image of your baby. You’ll see her moving, smiling, yawning – and even if her ears stick out like dad! “It’s important to remember that the nose and lips of the baby are very swollen, as baby has been lying in fluid all this time. Noses tend to be quite flat and that is for breastfeeding purposes, so they can still breath while suckling once they are out,” says Reyneke.

COST
The 3D/4D picture scan costs from about R500, which usually includes the service, a CD with pictures, a few black and white prints on thermal paper and a DVD of the scan.

BEST TIME TO DO IT
Between 25 and 32 weeks as baby has developed fatty tissue and looks less skeletal

What you need to know

HOW OFTEN SHOULD I BE SCANNED?
“Being scanned at every examination is not acceptable unless there is a medical indication for it,” says Dr Muller. “Your nuchal scan and foetal anomaly scan are vital and one or two scans after 26 weeks to check growth and placental health are acceptable.”

CAN A SCAN DETERMINE THE BABY’S BIRTH WEIGHT AND WHAT KIND OF BIRTH I WILL HAVE?
No, a scan cannot give an accurate prediction of the baby’s birth weight or determine how it will move into the birth canal or how strong your contractions will be. It can confirm if the baby is not growing properly, if the placenta is not functioning properly or if the baby is the appropriate weight for its gestation – all factors, which could inform your birth, plan and date.

HOW EARLY CAN A SCAN CONFIRM MY BABY’S GENDER?
Between 11 and 16 weeks, foetus’ genitalia on ultrasound look very much the same. The clitoris can be quite prominent and the penis is small. ”Depending on the position of the baby and the mother’s weight, we can predict the gender with 70 per cent accuracy at 13 weeks,” says Dr Muller. “From 16 weeks the genitalia are usually easily distinguishable.”

SHOULD I HAVE A FULL BLADDER TO HAVE A SCAN?
“No,” says Dr Muller. “You don’t need any preparation before a scan these days. Some women can feel nauseous lying on their backs, so if you feel strange while having a scan, tell your doctor so they can shift your position.”


Is Ultrasound safe?
It’s been proven that the recognised ultrasound machines we use for
Pros and cons of scanning
While picture scans leave you free to worry about baby showers, baby rooms and birth plans, patients must realise that scans are firstly a medical examination, says Dr Muller. “While it is devastating, a diagnostic scan does not always deliver good news and parents need to prepare themselves for this eventuality. It’s not all about getting pretty pictures.”

If an ultrasound does reveal a problem you will be offered counselling to help you decide the next step to take or to help you prepare yourself mentally and emotionally for when your baby is born. Not all problems lead to miscarriage or abortion and, armed with knowledge, your doctor will be able to manage your pregnancy and the birth better.

Some potential problems, such as the position of the cord, will enable your doctor to take prompt action that might save your baby’s life. An ultrasound is only as good as the person performing it and the correct position of the baby.