Congratulation ryukeong.

She got to eat balance diet, try to avoid fried, oily, processed food, cold n etc....

consume enough of fluid. Do not eat a lot or over on anything that ppl said is good, everything moderately will do, she need all sorts of nutrients and minerals thru healthy food n fruits.

Fetus dun really consume from mummy's food so no need to eat extra more for your fetus, more of mummy's craving for food she wanted to eat, due to hormonal changes it varies from one and another. So if mummy r healthy, fetus also healthy.

good luck and all the best

Hey Ryukeong, firstly congratulations on your first born!

I am going through a similar situation as you (my first born too, first trimester) and I found these foods help:

Dairy Products. During pregnancy, you need to consume extra protein and calcium to meet the needs of the growing fetus
Legumes
Sweet Potatoes
Dark, Leafy Greens
Lean Meat
Fish Liver Oil

I also realise that if your wife eats every 3-4 hours a day, the vomiting feeling will be heavily minimised. So make sure she takes in food in those times and she'll feel much better!

Good luck and Take Care