Labour is an apt name for the usually hard and tiring process of giving. However, only the second stage involves active physical effort from the mother, and even this is not always necessary – some babies arrive without their mothers consciously pushing them out. The uterus, which is at that time the largest muscle in the body, contracts regularly and strongly for a number of hours.
Asprogresses, these contractions become even stronger and closer together. During this time the energy stores in the mother’s body are being used up, so it is not surprising that most new mothers feel exhausted at the end of . Fortunately recovery is fairly rapid, helped no doubt by the joy of having a healthy baby.
The length of labour can vary considerably and there are few ways of predicting how long an individual labour will last, but there are a few guidelines. First babies usually take longer (about 12 hours) to be born than second or subsequent ones (about 6 hours). But labours can vary from one hour to more than 24 hours. In general, however, a second labour is likely to be shorter and easier than the first, because fewer contractions are needed for the baby to be born. It is estimated that on average about 150 contractions are required for the first baby, about 75 for the second and third, and only 50 for the fourth and fifth. Doctors consider that true or ‘active’ labour starts when contractions become regular and painful, but regular contractions often begin many hours before they become uncomfortable, let alone painful. Throughoutthe uterus contracts about every 15 to 20 minutes or so, for less than half a minute at a time. Usually these contractions (called Braxton Hicks contractions) go unnoticed, although occasionally they may be felt as a tightening of the uterus or abdomen. In late , they become stronger and in the last few weeks they may be strong enough to be noticeable and even to convince a woman that she is in labour. Sometimes she is right, but these obvious contractions may die down and resume their previous, milder pattern. This is known as a ‘false’ labour.
Although these false alarms are frustrating, the contractions of lateserve an important purpose by gradually and gently working on the cervix to prepare it for the . Before the baby’s head can pass out of the uterus and into the vagina, several things happen. Hormonal changes in the last few weeks of pregnancy make the cervix softer. The contractions which mark the beginning of labour start to draw up the walls of the cervix so that the cervical opening is on a level with the base of the uterus, a process known as affacement. The opening of the cervix then dilates. During most of the pregnancy, the cervix is effectively closed, with its opening only two to four millimetres wide. A width of ten centimetres is necessary to allow the passage of the baby’s head. Sometimes the dilatation happens so gradually that the cervix may be two or three centimetres dilated before the woman realizes her baby is on its way.