I believe in the thoery that it is better to have a suprise.  I know of too many people who have been told that they were having a girl & had a boy and vice versa.  I also know quite a few people who have become distressed at this.  Of course it is up to you if you want to know the sex of your baby.  Just remember that the main thing is that both you and the baby are fit & healthy and that the baby is loved.

Hope that everything goes well.  Good luck at your scan and hope that you get good pic's.

Babies external genitals are developed by the end of week 11. The sex of the baby can only be determined by the presence of external genitals so like others have said it depends on how good a view the radiologist can get. In the UK it is usually determined on the 20 week scan.
I found this site: http://www.mayoclinic.com/health/prenatal-care/PR00112
I hope it helps.

How exciting.  Congratulations.  At 18 and 26 weeks.  Accuracy depends on several factors: baby's cooperation, gestational age, technician's ability, etc. 

Hi there,

Well this also depends alot on how experienced the radiographer is and also the position of your baby.

With my 3rd child we were lucky enough to have a scan at 14 wekks and her legs were wide open so of course we had to ask . . . .HEHEHE

However with my other two i was 18-20 weeks . . . . Dont be in too much of a rush . . . Even if they do have a guess it is just that a guess! and i agree with Deb the only way to know for certain is via an animo and they aren't the most pleasant of experiences.

Cheers Kellz

from about 16 weeks aprox

Between 18 and 26 weeks. And even then you may not be able to see :)

Hi
Don't be too anxious to know the sex from a ultrasound
With Megan we were told 98$ chance it was a boy
Prob is if hormones are still going into a girl she can look like a boy
Unless you are doing amnio there is no sure way
Sorry
Luv Deb