Fetal Anatomy Survey
It is recommended that all pregnant women have an ultrasound of their fetus and pelvis at 19-20 weeks gestation; with the optimal time for most women being 19 weeks. The principal aims of this ultrasound examination are:
- The confirm the fetus is alive
- Measure the fetal size
- To detect multiple pregnancies
- To assess the placental position
- To assess the amniotic fluid volume
- To review the basic structures of the fetus
- To assess the maternal pelvic structures
Why is this examination performed at 19 weeks gestation?
At 18-20 weeks gestation we are usually able to obtain optimal views of the fetus and the uterus. Measurements of the fetus are still very useful to confirm pregnancy dating if this has not been performed previously. As the fetal structures are generally formed an assessment for severe structural fetal anomalies may be made. The fetal size at this time is such that it can still fit onto the screen to facilitate imaging of the fetal structures.
Do I need a full bladder?
Some urine in your bladder is helpful to outline the cervix and the relationship of the placenta with the lower uterus. Urine in your bladder also elevates the uterus from the pelvis into the abdomen to facilitate imaging of the fetus.
However, you do not need a large volume of urine and drinking 1 glass of water 30-60 minutes prior to your scheduled appointment is all that is required.
Can I find out the gender of my fetus?
An ultrasound is not 100% accurate in determining the fetal sex. If you wish to know the gender of your fetus at this ultrasound examination, please let us know (also if you do not wish to know) and we will endeavour to determine this for you during the scan.
Will I receive pictures of the pregnancy?
We will provide you with images of your baby’s face, and usually hands or feet.
3D and 4D imaging of the fetal face is routinely performed. Whilst we usually are able to obtain nice pictures of the fetal face for you, on occasions due to fetal position of if your body type does not permit optimal imaging, we will not be able to provide this imaging.
Womens Imaging Services has commenced using TricefyTM, an image sharing tool that enables selected images of your obstetric ultrasound to be sent directly to your mobile telephone at the completion of the assessment. These images will remain active on your mobile device for 90 days, after which they will no longer be accessible to you. We therefore strongly recommend you download the ultrasound images from your mobile telephone to your computer soon after the examination, where they will be yours to keep and share indefinitely. The TricefyTM image sharing platform enables you to email or text images of your pregnancy to family and friends.
We no longer provide thermal prints or DVD imagery with this ultrasound examination, in keeping with current technology advancements.
What types of fetal problems are able to be detected at this examination?
A fetal anatomy survey cannot detect all fetal problems and the accuracy of the scan depends on the position of the fetus, the gestation and maternal build. For larger women with increased body fat the diagnostic accuracy is reduced.
Ultrasound is quite accurate in the detection of conditions such neural tube defects (anencephaly and spina bifida) with a detection rate of 90%. For conditions such as cardiac defects the detection rates are much lower (25-50%). It is not possible, even in the best of hands, to detect every fetal problem: the main reasons for the fetal anatomy survey are to ensure the pregnancy dating is correct, to assess the position of the placenta and to potentially recognise significant fetal structural problems which may alter the place, timing or mode of birth. No prenatal ultrasound examination can detect all fetal structural problems.
If your pregnancy is at particular risk of a specific fetal abnormality (eg family history of spina bifida), please let us know. Ultrasound cannot detect conditions such as cerebral palsy or autism. An unremarkable fetal anatomy survey does not guarantee that your baby will be “perfect”.
What will happen if a problem is detected?
96% of fetuses are structurally normal. 2% of fetuses have a major structural problem (such as a heart defect or spina bifida) and a further 2% have a minor problem (such as a facial cleft lip or distension of the collecting system of the kidney).
If we detect a problem at this time of the ultrasound scan we will inform you at the scan appointment. We will contact your doctor and discuss the findings with them and arrange further management (eg an appointment with a clinical geneticist, a paediatric surgeon, an amniocentesis).