No one knows what triggers labour but there are assumptions that it begins by a hormonal response, probably to triggers which come from the baby's adrenal gland. Once this happensa womans uterus starts contracting. They may not even be felt at first and could go on for hours without the woman even realising. The first a woman may notice is a dull ache or period type pains in her low abdomen or back. These contractions may be start off irregular , possibly only occuring once every half an hour or so. Over time they will become closer together and more painful. Remember that not all births are the same. Your 'waters' could break before the contractions start or afterwards. And in some cases, not until the baby has been delivered. At the start of labour your cervix is barely open (dilated); over the next 5 to 15 hours or so it dilates completely. This can be seen in the simulated birth video under the 'birth' category. As the womb contracts, the baby is pushed downwards and almost reaches the end of the birth canal (vagina), with the head (usually) about to be born first. Breech delivery are still possible vaginally but can often be complicated requiring a lot of exertise. The idea of contractions is to dilate the cervix to around 10cms so that the baby's head can fit through. This process takes time hence the reason why some women say they were in labour for days. In factreallabour doesnt begin until the contractions are coming every 3-4 minutes, lasting 60 seconds and the woman is 3-4 cms dilated. Sometimes, contractions may slow down, or even stop. Sometimes it halps to move around or change position, to get the contractions going. The actual birth of the baby is called stage 2. It's usually a lot quicker than the first stage. It can be very quick – lasting just a few minutes – or take up to two hours, and sometimes much longer. Actively pushing takes a lot of effort and can be very draining. It begins when the cervix is fully dilated (10 cms), and when the woman feels a very strong urge to push downwards. . The first part of your baby to be born is the top of his head – this is known as 'crowning'. A couple more contractions and the head will emerge, usually facing towards your back. Your baby's shoulders and head will then turn sideways. The baby's body then emerges. The umbilical cord is usually clamped and then cut at this stage, the cord does not have to be cut by a health professional if the woman requests otherwise. Stage three is the delivery of the placenta, and it takes from 15 minutes to about half an hour. As the baby is born, syntometrine (a drug which helps with the separation of the placenta from the uterine wall) may be given as an injection, usually in the thigh or buttock. A physiological third stage is when no drugs are given to aid the separation of the placenta, a process which may take slightly longer. This means the uterus contracts by itself, and expels the placenta and membranes. The cord is clamped and then cut when it stops pulsating, after the placenta is delivered.