ARE YOU READY FOR YOUR CLOSE-UP?
The lowdown on everything you need to know about your antenatal scans
What you need to know about all your antenatal tests
The appointments may only last 30 minutes or so, but ultrasound scans are defining moments in any pregnancy. Ultrasounds check your baby is growing and assess the risk of abnormalities, such as Down syndrome and spina bifida. Additionally, many mums-to-be don’t relax until they see that first image of their babies. Here’s what you can expect from your antenatal scans.
How they work
An ultrasound machine emits high frequency soundwaves through a handheld device called a transducer. They bounce off solid objects, such as bone and organs, but pass through fluids, and are converted into an image of your baby.
Usually, the first trimester screening (often referred to as the 12-week scan) takes place between weeks 11 and 14. At about 18 to 20 weeks, most women have a more detailed screening, the foetal morphology (or anomaly) scan.
Your scans will be 2D, but it may be possible to opt for a 3D scan – for more detailed pictures – or even a 4D scan for pictures in real time, rather than stills. Since these are elective services, they won’t be available everywhere, and the extra costs involved won’t be covered by Medicare or private health insurance.
Name the date
Although you may have pinpointed the night you conceived and have a date from your GP based on your last period, the 12-week scan provides the most accurate calculation of your due date.
Your sonographer will measure your baby from the top of her head to the bottom of her spine to confirm the due date. Babies grow at a set rate over the first 12 weeks, so the results are very accurate.
Remember to drink plenty of water before the scan, as this will give the sonographer a clearer view of your uterus.
The bigger picture
As well as giving you a timeframe for your pregnancy, the 12-week scan will check for multiple gestations, so this might be the first time you find out you’re carrying twins or triplets. The 12-week scan also involves a nuchal translucency
(NT) scan to check for chromosomal abnormalities, such as Down syndrome.
The NT scan takes an image of the baby to measure her length and the thickness of the pocket of fluid at the back of her neck.The result is combined with a blood test (which examines the levels of two specific proteins: pregnancy-associated plasma and free beta human chorionic gonadotropin) and the mother’s age to assess the baby’s risk level for Down syndrome. While this method has an accuracy rate of about 85 per cent, it can only indicate whether the baby has a high or low risk of abnormality; it cannot provide a definitive result.
The anomaly scan is an analysis of the structure of the baby to ensure she’s growing at the correct rate. It involves taking measurements of her head, abdomen and thigh bones. Your sonographer looks at her face (to rule out cleft lip) and spine (for defects such as spina bifida). The heart’s size and shape is also examined to ensure blood is flowing through it correctly, and makes sure her stomach, kidneys and bladder are working.
It’s ok to feel nervous
Going to have a scan can be both exciting and nerve-racking. It’s normal to feel scared, but your sonographer will always explain what or she is looking at. Your doctor will go through your results and answer questions about your options. It’s important to be prepared for any result, even during routine scans, but it’s equally important not to worry unnecessarily.
Under the microscope
As well as looking at the foetus, the ultrasounds check your uterus. At the second scan, your sonographer will look at the position of your placenta. If it’s near the top of your womb, it’s described as anterior, which is good. If it’s at the bottom, you’ll need further scans in your last trimester. If it doesn’t move away as your baby grows, you may have placenta praevia (where the placenta sits near or over the opening of your womb). You’ll be checked again at 32 weeks and, if it’s still in the way, you may be booked in for a caesarean. There will also be checks to ensure blood is flowing normally through the umbilical cord and that there is enough amniotic fluid.
Finding out the sex
This is usually possible at an anomaly scan, but if bub is in an awkward position, the gender may be tricky to confirm. Not all ultrasound centres or hospitals will tell you the sex; check their policy. And if you don’t want to know, make this clear early on.