Spontaneous labour especially for a first labour can start gradually. Crampy period pain and Braxton Hicks contractions can increase gradually and become early labour. It is possible to have a run of contractions each evening for several evenings in a row and then the next evening the contractions will continue. Contractions will then become more regular, stronger and last longer.
In many first labours the contractions will fluctuate. There may be a period of time where the contractions are very intense and then a period of time when there are hardly any contractions. Some first labours will be very efficient and regular contractions will continue once they start.
Contractions are like waves on the beach in the sense that some are stronger than others and they are not equally spaced apart. Midwives measure contractions per 10 minutes but contracting 2 in 10 is more likely to be 4 minutes, 6 minutes, 5 minutes, 4 minutes apart than exactly every 5 minutes. Timing contractions is easier if the beginning of each contraction is noted, as contractions last for different lengths of time.
Cervical Dilatation in the first stage of labour
The non-pregnant cervix is around 4cm long and the cylindrical canal is open just enough to let menstrual blood out. At the end of pregnancy, we expect the cervix to be around 2cm long. There is wide variation on how dilated the cervix will be. Some cervixes will be closed. Others may have dilated up to 3cm and shortened to 1cm in the “ripening” process prior to labour.
Once there are regular contractions the cervix will start to dilate. The first stage of labour is divided into the latent phase and the active phase. In the latent phase of labour the cervix dilates gradually from closed to around 3 to 4 cm dilated. The active phase of labour occurs after 4 cm dilated until 10 cm or fully dilated.
If the cervix has not shortened and opened up (i.e. ripened) very much prior to the onset of contractions then the latent phase of labour where the cervix dilates from closed up to 3cm dilated could take 24 hours for a first labour. Some women may have an even longer latent phase.
Between the latent phase and the active phase of labour it is possible to be having regular painful contractions while the cervix stays around 3 to 4cm dilated for anywhere from a few hours to almost 24 hours. At some point the contractions will intensify and the progress of dilatation will start again. For some women this increase in intensity will occur once the waters have broken spontaneously.
In the active phase we expect an average progress of 1 cm per hour dilatation. Progressing 4cm to 10 cm dilated could take around 6 to 8 hours.
Progress in labour varies with the individual but even the most efficient labours may take several hours. Some cervixes will dilate quickly during the middle of labour and then the progress will slow down towards the end. In other labours the progress goes quickly at the end of the first stage of labour as full dilatation is approached.
Second stage of labour
The second stage of labour occurs after full dilatation which is equivalent to 10 cm dilated. Sometimes it is possible for the cervix to be fully dilated but the fetal head needs to descend further into the pelvis before pushing can commence. This is known as passive second stage. We expect the head to descend enough for the pushing to commence within 1 to 2 hours.
Most women have to work very hard in active second stage to push their baby out. A strong expulsive effort is required to push baby's head up the ramp and around the curve of the pubic bone so the head will crown and start coming out of the vagina.
For active pushing, the abdominal muscles that are used to move firm bowel motions when constipated need to be engaged. Holding a breath helps to focus the pushing downward, long and hard, toward the bottom. The aim is to take a breath, push for as long as possible, let the breath out and then repeat this twice more, so that there are three pushes during each contraction.
Contractions tend to space out during second stage but the effort required is still like doing abdominal crunches every 5 minutes. It is not unusual to push for 1 to 2 hours for a first vaginal birth. There is a lot of elasticity in the tissues of the birth canal so that the force of pushing will push the head down. Once the contraction is finished the head will rock back up. Gradually the head will descend a little further with each push.
Once the top of the fetal head is visible at the vaginal opening it is possible for a labouring woman to observe the progress of pushing in a mirror. This can provide instant feedback on the effectiveness of the pushing.
For most of the second stage big pushes are required. When the head is close to delivery it will be distending the perineum and gradually stretching the perineum over the fetal head. At this stage small pushes with stopping in between are preferred. At the very end, as the head emerges from the vagina, breathing in and out without pushing will be all that is needed. This gradual transit of the head through the vaginal opening allows stretching to occur and reduces the risk of perineal tearing.
Once the head has emerged from the vagina, the neck is checked for any loops of cord that can be unlooped so that the cord does not tighten as the body is delivered. Around two thirds of babies will have cord around the neck and it usually doesn’t cause a problem. Delivering the head is usually the hard part and the shoulders deliver with the next contraction. Very occasionally the shoulders do not come out of the vagina easily and additional manoeuvres are required for delivery of the shoulders.
After baby is delivered, an injection of Syntocinon or equivalent is given to help the uterus contract down and reduce the risk of bleeding. The placenta can be delivered by fundal pressure so that the blood in the cord can be used for cord blood donation. The placenta can also be delivered by controlled cord traction with gentle pulling on the cord and a hand placed on the lower abdomen to ensure the placenta has separated from the uterus.
After the placenta has been delivered, the contraction of the uterus and the amount of bleeding is watched very closely. The perineum is inspected to see if any suturing is required. Baby can rest skin to skin on mother’s chest during this time. Baby will be weighed and measured and the task of acquiring breast feeding skills can begin.