From 36 weeks the uterus starts getting Braxton-Hicks (non-painful practice contractions) contractions. These are to about ¼ in intensity as compared to labour contraction. (15mmHg pressure as against 60mm Hg pressure in labour).
Normal Labor is that occurring after 37 weeks pregnancy. It should result in the spontaneous vaginal delivery of the baby within 24hr of the onset of regular spontaneous contractions. It is often preceded by a plug of cervical mucus (what is known as show) and a little blood as the membranes strip away from the external os. The membranes then rupture.
NORMAL LABOUR IS DIVIDED IN 3 STAGES:
The first stage of labor is the time taken from the onset of regular labour (uterine) contractions till the cervix is fully dilated. The cervix initially becomes shorter and softer (aka effaces) before it dilates. A satisfactory rate of dilation is approx 1cm/h. The first stage generally takes up to 12hr if it is the first child (primipara), and approx 7.5 hr if it is the second or onward pregnancy.
WHAT WILL THE DOCTOR DO DURING THIS TIME?
During the first stage a doctor or a nurse will check maternal pulse, BP and tempo every half-hourly; the uterine contractions will be assessed every 15min for their strength and their frequency (ideally 3-4 per 10min, lasting up to 1min). A vaginal examination may be carried out every 4hr to assess the degree of cervical dilation, the position and the station of the head (or the presenting part) and note the degree of moulding. Maternal urine may be tested every 4-hours for ketones and protein. The fetal heart rate is measured (if not being continuously monitored) every 15min. The rate is noted before, during and immediately after a contraction.
The second stage is the time from complete cervical dilation until the baby is born.
The mother will have a desire to push and will use her abdominal muscles with the valsalva manoeuvre to help move the baby. As the head descends, the perineum stretches and the anus gapes. Normal time for this stage is 45-120min in primi, 15-45min in a multipara. The aim is to prevent a precipitate delivery (and so intracranial bleeding by pressure over the perineum. The placental cord is tied at this stage.
The third stage of labour is the delivery of the placenta. As the uterus contracts to a 20 week size after the baby is born the placenta separates from the uterus. It then buckles and a small amount of bleed behind the placenta aids its removal.