Hi,
Thanks for using healthcaremagic.
It is not mentioned exactly what is the shadow and which area is the shadow seen so its difficult to comment on it. Although, the baby's spine itself can cast a shadow. In
ultrasound, we see a shadow behind any bony structure/calcification. The spine is a bony structure so it can cause shadowing by itself. If its because of the spine, there is nothing to worry.
About the head, minor changes are accepted and there are standard measurements for the head upto 40 weeks of
pregnancy. The measurement is classified as percentile taking a group average. If the head circumference is more than 97th percentile, then it is called
macrocephaly. Isolated macrocephaly is not of any clinical significance.
In your case, as the sonographer told its slightly big I think it is within 50th and 97th percentile, so the size will be within normal limits. If you can mention the exact head circumference I can check the graphs and tell you accurately whether its big or not.
You can get back to me with more details and I would be happy to help.
Hope it sorts your problem.
Regards,
Dr. Pankaj Nagori
Specialist Radiology