When can I find out the gender!? This is a question I am asked on an almost daily basis. Ultrasound is most definitive in the second trimester. There is however a method sonographers use to determine gender between 12 - 14 weeks. This method is known as the 'dangle of the angle'.
In the first trimester both baby girls and boys have a nub that projects from the pelvis. The majority of mistakes are made when a tech assumes the nub means boy. The angle is very important. A baby girl will have nub that appears to run parallel to her sacrum (spine). A baby boy will have a perpendicular nub projection, just like in the image below. You must remember that ultrasound is not 100%, but with a skilled technologist, and a cooperative baby ;), you can have great accuracy with it!
There are blood tests available for gender as early as 9 weeks. The NIPT is a test ordered by your doctor, this is mainly to rule out genetic abnormalities, but gender is included at 99% accuracy. There are also blood tests available for purchase all over the web, the most popular being Sneakpeek, this is less accurate but still about 80-90%. Blood tests are great gender options, but there is nothing like seeing your little one wiggle around on a big screen!