The best gender clues via nub guessing is from late 12 weeks (more like 12w6d) through 13w6d. Obviously anything beyond 13 weeks is good too. Ramzi theory is bunk- I had a classic ramzi girl baby with my DS3. I've even seen Dr. Ramzi himself guess wrong several times.
[emoji170][emoji1379]DS1, [emoji577]DS2, & [emoji602]DS3[emoji170]
[emoji166]EDD 9/30/2017 [emoji1317]for pink[emoji166]
https://lmtm.lilypie.com/Tub9m6.png