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Date of last update: 10/14/2017.

Forum Name: Obstetrics

Question: trans cerebellar diameter at 19weeks 4 days pregnant?

 nazza - Fri May 01, 2009 5:39 am

I am 19 weeks and 4 days pregnant. My U/S today confirmed this. It also showed that the baby's trans cerebellar diameter is 19mm - consistant with 18 weeks, 4 days. What does this mean?
 Debbie Miller, RN - Fri May 01, 2009 1:21 pm

User avatar Hello,
In early pregnancy, growth of the fetus is very consistent, allowing ultrasound dating to confirm or clarify calendar dates which can vary quite a bit. By measuring certain bony structures such as skull and leg bones. This measurement is of the head here is not significant. It could mean your baby has a slightly smaller head than "average" but remember that average means there is a range with half larger and half smaller. This can be perfectly normal, especially in the absence of other concerning findings. It has not been shown to be a good indicator of chromosomal abnormality. This might prompt your doctor to repeat an ultrasound in a few weeks to see if there is any grown delay over time.

In days past when we did not do ultrasounds, we would never have known about such a measurement and chances are everything would still be fine. Ultrasound is a wonderful tool, but not perfect. Often it just suggests some things to watch for as time goes on.

Good luck with the pregnancy.

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