YADNBU and your dh is being an arse and a sexist arse at that! Women are incapable of making a decision during pregnancy are they? Well, I don't know how I coped with running a house, holding down a job and running a small business through five pregnancies then!
FWIW, the only time I ever found out the sex was on ds4. I already had three boys and was kind of hoping for a girl. So I found out he was a boy and spent the next 11 weeks crying and feeling hard done by. Then he was born and it really didn't matter what gender he was, he was a gorgeous baby and is still absolutely adorable three years on.
This time, I refused to find out. At the 20 week scan, I told the sonographer that I didn't want to know and that was that.
Then at 28 weeks, I had a crash caesarean section and hysterectomy. She is a little girl.
BUT after the shock I got (placenta accreta, massive bleeding, life-threatening) I really didn't care what she was, so long as she was OK and I was so thankful that my obs saved her life and my life. For days I called her "he" as to me, babies were boys! I did find it odd, that knowing that she was so premature that peoples first response was that I must be over the moon that I had a daughter but when you see your baby in an incubator, with wires and tubes coming out of his/her tiny body, you do not care about gender. Thankfully she is doing well now. And I am very glad that I didn't find out!