Labor begins when your cervix starts to open, or dilate. The uterus contracts at regular intervals, and the abdomen becomes hard. Between contractions, the uterus relaxes, and the abdomen becomes soft.

How labor begins
It is difficult to define clearly the moment of onset of labor and to predict the exact sequence of events. There is a period of prelabor, called lightening, during which the baby falls lower toward the cervix. Lightening creates pressure on your bladder and makes you need to urinate more often. Prelabor can last for several days or weeks.

The contractions you experience during the prelabor phase may make you think that you are in labor. Time the contractions from the beginning of one to the beginning of the next. If they don't change in frequency or length and are not regular, you are probably in "false labor"; if the contractions become more frequent and continue for more than an hour, you are probably in labor. In the early stage of labor, they will probably last for 30 to 60 seconds.

If you are at term and in labor, you will probably also experience

• The beginning of the opening of the cervix to allow the passage of the baby. As the cervix begins to stretch, it may release a plug of bloody mucus that has blocked the cervix during pregnancy.
  
  
• The rupturing of the amniotic membrane, most commonly after contractions have started. The rupture may come as a gush or as a slight dribble of fluid, but it won't hurt. The membrane may not break until you are in active labor at the hospital—but when it does, it is time to call your health care professional.

Early phase of labor
At home or in the hospital, your health care provider will ask you about your labor so far—about your contractions and whether your membrane has broken. You will be asked, too, about bowel movements. If you have not had one recently, you may be given an enema or a suppository. A urine sample will be taken to test for protein and sugar.

During an examination you will be checked to determine the baby's position and heartbeat; for your blood pressure, pulse, and temperature; and to see how much your cervix has opened. You will have periodic vaginal examinations, and the fetal heart rate will be monitored either periodically or continuously.

In the early stages of labor, if your primary health care provider is not there at all times, he or she will be kept informed of your progress and will be notified of any problems. In the later stages, the primary provider should be present all the time.

During the first stage of labor the baby drops, usually head downward toward the cervix, stretching it. If the amniotic membrane did not break at the start of labor, it will probably rupture now. The stretching of the cervix causes contractions of the uterus, which in turn push the baby down and stretch the cervix more. Then the cycle begins again. In the early part of labor, the contractions might occur only once every 30 minutes.

During this stage of labor you will probably be encouraged to relax during contractions, rather than bear down. Bearing down now will not help the progress of delivery.

The length of labor with a first baby averages 12 to 14 hours; after the first baby, labor averages 7 hours.

If labor needs to be induced
If your health or the health of your baby is at risk, your labor may need to be induced (started by the doctor). Induction may be selected for numerous reasons, including the following:

• Amniotic membrane has ruptured without the onset of labor.
  
  
• Placenta has been delivered before baby.
  
  
• You have diabetes.
  
  
• You are 2 weeks past due your due date.

The contractions of induced labor may be more painful, because they start so suddenly. Induced labor may also be more likely to require the use of pain medication.

If induction is needed, your doctor will tell you when to go to the place where you will deliver.