Are contractions more likely to start at night?

This fabulous hormone interacts with oxytocin to promote contractions, and melatonin is the hormone that is responsible for encouraging us to go to sleep! So clearly it reaches it's peak during the dark hours, making us more likely to go start contracting in the evening.

Why do I have more Braxton Hicks at night?

Some women notice that Braxton Hicks contractions occur most often at night—possibly because moms-to-be are more relaxed and observant. Also, you might have a full bladder or be sexually active at night (both of which can trigger Braxton Hicks).