Dr Rahul Sen | Specialist care for birth and beyond | Sydney, Australia

Rooms : Edgecliff 02 9363 9474
Macquarie Street 02 9221 2600

Ultrasound Scans

Your pregnancy is dated from the first day of your last menstrual period (LMP), which is around two weeks before actual conception.  I shall confirm this with a dating scan at around 8 weeks.  Early (8-10 week) ultrasound scans are generally more accurate for dating your pregnancy than later scans.

At 12-13 weeks you may wish to have a screening test for Down Syndrome (Trisomy 21) if you have not had the Harmony test, known as the Nuchal Translucency Test.  This involves an ultrasound of the baby’s neck and nasal bone, The test is best performed in specialised obstetric ultrasound centres and should be performed in conjunction with a special blood test, done at 10-12 weeks.  If these tests show a high likelihood of a problem I shall discuss further testing with you, including Chorionic Villus Sampling (CVS) or Amniocentesis.

I shall arrange for you to have a specialised ultrasound scan at 18-20 weeks, known as the morphology scan or fetal anomaly scan.  At this scan a detailed review of your baby’s anatomy is performed, to make sure that there is no major abnormality.  The majority of major malformations can be detected in this way, as well as some other problems, but please be aware that the background rate of abnormalities is around 3%, and that no single test can detect 100% of problems.  It is also important to remember that while we are quite good at checking fetal anatomy, it is almost impossible to check on fetal function prior to birth.

I usually scan your baby at each of your visits, however I usually recommend an external scan at 36 weeks to recheck the baby’s anatomy and to check on the baby’s growth and placental function.  I may also discuss further growth scans in the last trimester of pregnancy if I am concerned about the growth or wellbeing of your baby, or if you have high blood pressure or diabetes.  If the placenta is low-lying at your 19 weeks scan then this will be rechecked with a further ultrasound at 32-36 weeks.

3D scans can provide great views of the baby’s face.  The best time to perform a 3D scan is at 30-33 weeks.  This is a fun scan and is not medically necessary.  I have organised for an experienced sonographer, Lily, to perform 3D scans at around 29-30 weeks in my Edgecliff rooms.  Please book in for this scan at your 24-28 week consultation.