Hm. I'd say, buy her chocolate. (kidding . . . kind of . . .)
Hi and welcome to the forum. And welcome to fatherhood! Being a parent is a great thing and you are going to love it,
Here are my suggestions:
What I wanted most from my husband is that he would listen to me. All of my many complaints or observations about how my body was changing, how I was feeling, how the books said the baby was growing, etc. I also needed my husband to be patient with me. Hormones are tough during pregnancy and at times, a woman can be unreasonable, grumpy or sad for no real reason. Patience is really key at those times.
You should help her out in any way you can. Carry in the groceries, offer to do some things around the house, give her neck, shoulder and foot rubs, (this is a big one) TELL HER SHE LOOKS BEAUTIFUL!!
Do not stare at her butt and comment that it is getting large. Big no no to make fun of a pregnant woman in any way.
Do not tell her she needs to exercise. Instead, say "honey. It is a beautiful night. Would you like to go for a walk with me?"
Do not tell her to eat spinach. Instead, say "honey. I made this delicious spinach dip. Want some?"
Before the baby is born, write her a letter telling her how much you love her and have enjoyed being married so far. She'll treasure that.
good luck and happy baby
thanks for your valuable comments