Skull/Nub Theory at 10 Weeks?

Nicola • Mommy to the most loved, beautiful angel in heaven.. Giovanni Antonio Brown born January 21st, 2017 👼🏽❤️ My beautiful rainbow baby Ezra was born December 20th, 2017 🌈👶🏽💙 now expecting baby #3 12/2021 🥰
I've been trying to do the skull or nub theory on my rainbow baby, but I can't figure it out so maybe one of you could help me?
Baby was measuring 10w 4 d, heartbeat was 171