You are a very important person
During pregnancy the mother of your baby is likely to be more tired, uncomfortable and emotional than usual. She will not only experience changes in her shape but also in her skin and hair and may feel less attractive.
You can give her the support, attention, understanding and love that she needs. You can make her feel beautiful and special. Give her lots of attention, encouragement and offer to help around the house. Surprise her with fresh flowers from time to time.
Her libido may be less in pregnancy. Don't worry it is usually only temporary!
It is a good idea if you can attend the antenatal classes to support your wife / partner in the classes and can learn how to support her in childbirth.
Also if would be good if you could attend at least one antenatal visit with her. This is so you can get to know me, and I you. Also if you have any questions or concerns please feel free to raise them.