You really could be confused for thinking “Well I’ve had a nice normal NIPT and a normal Early Morphology Scan – seriously is there more these people need to test for?”
Well, yes, there is.
As good as the Early Morphology Scan is it is performed, well, early on in your pregnancy. Your baby isn’t simply big enough to identify some problems, so yes; you do need the 19 week scan. This scan can rule out:
- Significant Brain Abnormalities,
- Cleft Lip and Palate,
- Spina Bifida,
- Lumps and Bumps (as we doctors say) in the Chest,
- Significant Heart Abnormalities including mixups of the major vessels that enter and leave the heart,
- Hernias or holes in the Diaphragm or Abdominal Wall (apart from those that are supposed to be there),
- Problems with the Liver, Kidneys, Bladder, Stomach or Intestines
- Abnormalities of the Limbs, and
- Abnormalities of the Placenta and Umbilical Cord.
The ultrasound people also check the Amniotic Fluid volume as Amniotic Fluid is your baby’s urine so a normal volume means your baby’s kidneys and bladder are functioning normally.
In many instances the 19 week scan can pick up issues that need treatment – usually surgery – after birth. Cleft Lip and / or Palate is a good example, as is a Diaphragmatic Hernia or some Heart issues. While diagnoses like this can be very confronting it is really useful to know about them so that we can – if needed – monitor your baby more closely in the uterus and organise any treatment that might be needed after the birth well in advance of the birth. Some kids don’t need surgery but require ongoing scans and specialist follow up after the birth (I’m thinking some Heart and Kidney problems here).
Much more rarely – especially since we do have a good look at your baby at the Early Morphology Scan – we find something catastrophic at the 19 week scan. Spina Bifida and / or some Brain abnormalities are examples of such problems. Obviously this can be an incredibly confronting and stressful situation.
Ok. I’ve had a normal Harmony Test, a normal Early Morphology Scan and now a nice normal 19 week Morphology Scan. I’m all good now?
Obviously having all of these tests and scans come back as normal is immensely reassuring but – again – we still can’t offer money back guarantees. The 19 week scan – even in the most expert hands – can occasionally miss abnormalities such as some of the more subtle Heart Abnormalities. Also some abnormalities may not be apparent at 19 weeks but can appear later on in the pregnancy; for instance various blockages in the Kidneys, Bladder and tubes that connect them.
And there are simply some conditions – I’m thinking of more rare genetic problems – that simply don’t show up on ultrasound at all.
These are among the reasons we like to get an experienced paediatrician to check your baby after it is born.
But wait, there’s more…
Nobody expects the vaginal ultrasound probe (have I mentioned I’m glad I’m a man?).
It is now standard to offer you a vaginal ultrasound at the time of your 19 week scan. This is for two reasons:
- To assess the closed length of your cervix. This is important because your cervical length at 19 weeks is the best – of a bad bunch, to be fair – predictor of your risk of giving birth prematurely. A closed cervical length of more than 25 mm at 19 weeks is associated with a low risk of giving birth prematurely. If your cervical length was, say, 15 to 25 mm we might give Progesterone pessaries in order to reduce the risk of a preterm. Depending upon the circumstances a length of less than 15 mm at 19 weeks may necessitate us placing a stitch around your cervix. This is called a cervical cerclage. If your cervix is short at 19 weeks we would also organise follow up scans of your cervix until around 32 weeks gestation or so.
- To measure how far the lower edge of your placenta is from your cervix. You have a Low Lying Placenta (LLP) if its lower edge is less than 20 mm from the upper end of your cervix. Now most – a good 90 percent – LLPs move away from the cervix as the lower part of your uterus grows and develops over the second half of pregnancy so a LLP is only rarely a problem. We usually perform a third trimester scan around 34 weeks just to make sure your placenta really has moved. A placenta that remains low or completely covers the cervix is called a Placenta Praevia and that is a topic for another day…