If your having an ultra sound at 16 weeks like I had to due to cervical issues if the baby is in the right position they are also able to tell then. I opted out of them telling me and me waiting until my 20 week appt ( im 19 now) because I wanted my husband with me
My midwife tried to look at our 16 week appointment, but Baby was too wiggly to see. But she said you can see it as early as 15 weeks so long as baby cooperates
Early as 13 weeks with a blood test. Normally doctors do it around 20 weeks. You might be able to do a 3D one but it still could be early.