What causes Braxton Hicks?

In the beginning of pregnancy these contractions strengthen the uterus, where the baby is accommodated. Later they are preparing the region for the labour, by thinning it out and opening up the cervix. Braxton Hicks contractions also improve the flow of blood and thus oxygen to the placenta and the growing baby.

See also:
Braxton Hicks – Description
Braxton Hicks – Distinguished from labour
Braxton Hicks – When to worry