They can track and monitor the growth of the baby and also detect any congenital abnormalities.
When excluding those scans where a prediction could not be made, success rates increased to 91%.
Looking at my ultrasound photo, which you can see below.
Other markers are nasal malformation, cleft lip and palate, and head abnormalities such as microcephaly.
After buying many many girly items.
Conclusions: Sonographic gender determination provides high success rates in the first trimester.