The best time to take a birthing class is usually at the end of the second trimester (23-26 weeks) or the beginning of the third trimester (27-35 weeks). When to start a birthing class might also depend on what type of birthing class you decide to take and whether it is a multi-week series or a day-long crash course. The sweet spot for most people is to take the class late enough in pregnancy that the information and techniques are still fresh in your mind when you go into labor, but not so late in pregnancy that you risk going into labor early before you can attend the class.