Not all dads-to-be are eager to go to prenatal classes. They might not feel the classes apply to them, and may fear that they will be asked to do exercises that they find embarrassing.
If your partner is reluctant, discuss it with him, pointing out what the classes are for and why you feel that you need his support. You could explain that you want him to be informed about labor so that he is not anxious in the delivery room. He might find it useful to talk to male friends who went to classes when they were expectant dads. Classes may include some sessions with men and women together and others where the women go on their own, for example to practice breathing techniques, while the men have a separate session where they can share any concerns. If time off work is an issue for your partner, ask for a list of what topics will be covered each week and pick those sessions that you think are the most relevant for him. If your partner is well informed, he'll feel more involved in the pregnancy and more confident in helping you during labor and birth.