A contraction is a tightening of your uterus. The uterine muscle can contract at any time from mid-pregnancy on, and those contractions might feel like nothing at all, or they might be completely overwhelming.

Your uterus is a large muscle, and just like any other muscle in your body, it will flex when it’s stimulated, Hormonal changes can start contractions—but how you experience contractions depends on your pain threshold and what type of contraction you're actually having (yep, there’s more than one kind). In the first stage of labour, your contractions gradually open your cervix. In the second stage of labour, they ease your baby down through your vagina and out. In the third stage of labour, they dislodge your placenta and seal off blood vessels, as your uterus contracts down.