Thisvideo is for educational purposes and has been chosen as it reflects my experience of giving birth. By the end of pregnancy, the womb has become a big, muscular sack. It's been a home for the baby for nine months. Now it needs to push that baby out into the world. Most labour pain comes from the powerful squeezing of these womb muscles. These are called contractions and they have lots to do: 1. Stretch open the cervix (neck of the womb) to 10cm wide (the size of most babies' heads.) This stretching is called the First Stage of labour and it takes about 10 hours. We may start by getting contractions lasting for 30-60 seconds every 5-20 minutes. In between contractions, there's usually no pain, so we can rest. As labour continues, the contractions become more frequent, more intense and longer lasting. The feeling is difficult to describe and once it's over, it's difficult to remember. Most people say the nearest thing to it is extremely bad period pains. 2. Contractions also have to swivel the baby round so it's facing the mother's spine. This is the easiest way out. 3. Then they have to push the baby out through the vagina. This is the Second Stage of labour and takes about 1-2 hours. At this point the mother can start pushing too, using her tummy muscles along with the womb to push the baby out. 4. Finally, the Third Stage is where the placenta and umbilical cord come out. These bits have attached and fed the baby inside. Most mums are too distracted with their newborn to notice this stage. All this is heavy work. Think how your thighs feel even after a short run. Our womb muscles have to keep working out for an average of 15 hours. Phew. No wonder it hurts.