With the help of an ultrasound...yes.

My gynecologist just told me that we can use an ultrasound to help determine the sex of the baby after 20 weeks of pregnancy. However, it is not 100% accurate and the image is only verified when the child is born.

I've been told that with an ultra sound if it says boy then it is deff a boy but if it says girl than it may still be a boy. So if your ultra sound comes back with boy then it is but if it says girl it may still be a boy.

A 'boy' can still be a girl. The cord could be between the legs and be mistaken for a penis. Therefore, what is assumed to be a boy could very well be a girl whose cord is in the way.

I think the intended question of "blezzon" would be more along the lines of PRE-determining the sex of the baby.

There are many books and myths and tecniques out there... but I would not count on any of them to really work. I've not tried any myself... but my friend (a mother of 3 boys) has to no avail.