No my doctor told me 4d ultrasounds are a waste of money because the private area isn't formed yet you wouldn't know the sex until 18-20 weeks
That's not true. It's possible but they may not feel comfortable giving an awnser just yet. Most start doing gender at 14 weeks. I went for my son at 15 weeks and they had no problems telling gender at all, it was very obvious.
I didn't do my 4d until 15 weeks but they were able to tell it was a boy I was even able to tell. It was very obvious. Most 4d placed won't do gender check until 15 weeks since gender area isn't formed until then
3D done at 16 weeks. That's the earliest my OB will do them, but 14 weeks to 20 weeks is normal. 13 weeks is a little early in my opinion. But hey, it's your baby and body.
I wouldn't run and buy anything gender specific based on an ultrasound at the 13 weeks. I'd wait till the anatomy scan.