6 – 18 weeks
What is your due date?
Maybe you have seen the little ‘blue line’ however, seeing is believing. Perhaps you are uncertain of your dates or simply cannot wait until your NHS 12 week scan. Whatever the reason, an early dating scan can give you peace of mind that all is well with your pregnancy and also ensure that you don’t miss out on the early first trimester screening tests that are available. A scan can also help you bond with your baby and help you to relax and start enjoying being pregnant.
The dating ultrasound scan
This scan can be carried out from 6 weeks to 18 weeks. The most accurate time to date you pregnancy is after 8 weeks through to 13 weeks.
We ask that you to fill your bladder by drinking a pint of water before the scan. This makes it easier to see the uterus and ovaries as the full bladder pushes away the overlying bowel area. On some occasions it is still difficult to see and so we may ask if a more detailed internal ultrasound scan can be done trans-vaginally. This is a simple procedure and does not cause any pain or harm to the pregnancy.
The scan will:
- confirm pregnancy viability, in other words that there is a heartbeat seen.
- confirm the gestational age of baby. A measurement of the baby from head to bottom or Crown Rump Length provides an accurate estimate of gestational age and expected date of delivery. However, after 14 weeks we measure the baby’s head to ascertain the gestational age.
- check the number of fetuses and chronicity or type of multiple pregnancy. This is whether they share the same placenta which will highlight the need for closer monitoring of pregnancy. Approximately 2% of natural conceptions and 10% of assisted conceptions result in multiple pregnancy.
- Identify potential pregnancy problems and severe abnormalities. After 11 weeks the baby’s head, body, arms, legs, stomach, bladder and cord insertion can all be seen, ruling out a large number of major structural abnormalities including anencephaly, gastroschisis, exomphalos and megacystis.
The pictures and list below outline what we might expect to see in the normal early stages of pregnancy:
A small gestation sac can be seen in the uterus measuring approximately 3-4 mm
From 6+ weeks a small gestation sac and possibly a small yolk sac can be seen within. However, closer to 7 weeks and measuring only a few millimeters, a fetal pole(s) can be seen. This is still very early but if a heartbeat is seen then the chance of pregnancy continuing is approximately 78%. If the heartbeat is not seen we would rescan at a later time.
Baby grows rapidly and now measures between 10-20 mm and a heartbeat can be seen clearly.
Baby now measures between 35-40mm and with heartbeat seen and baby measuring correct for your dates, the chance of the pregnancy continuing is 97%.
Baby is now measure 45mm+ and clearly has a distinguishable head, body, arms and legs. The heart can be seen beating in the chest area and the stomach, bladder and cord insertion are visible. The baby from this time onwards just has to grow and get bigger and stronger. At this stage the chance of the pregnancy continuing is 99%.
After 14 weeks
Due to baby being bigger, we now measure the head circumference (HC), abdominal circumference (AC) and femur length (FL) to give the most accurate gestational age.
The dating scan ultrasound results
A clear explanation of the procedure and what has been found during the scan will be given to you by our clinical specialist throughout the scan. We share everything; you will see what we see.
A full report detailing all aspects of the scan is given to you and can be added to your obstetric records. It is good to share this result with your midwife.
Should you wish, we can also discuss further screening tests for Downs Syndrome and other anomalies that are not consider more accurate than those available through the NHS.
You’ll also be given pictures and depending on the babies age you can also request a 4D image.
On very few occasions we do find problems. It is always so hard when this happens, but we are there for you fully, to answer all of your questions and hold your hand through the options that arise. We will of course make all arrangements for your follow-up care either with our own specialist consultants or with your own care professionals.