Stages of labour (birth)

• Introduction to labour
• Stages of labour
  • Stage 1 – Cervical dilation
  • Stage 2 – Expulsion
  • Stage 3 – Delivery of the placenta

 

Introduction to labour

Labour is the process of passage of the foetus and placenta from the uterus, through the vagina, to be external to the mother. It is part of the process of parturition, which refers to labour, delivery and birth. Parturition requires the dilation of the cervical canal to accommodate for the passage of the foetus, as well as contractions of the uterine muscle wall that are strong enough to expel the foetus.

Stages of labour

There are three distinct stages of labour:

• First stage – dilation of the cervix.
  • Latent phase (0-4 cm dilated)
  • Active phase (4-10cm dilated)
• Second stage – fully dilated till expulsion of the foetus
  • Descent of the head
  • Pushing phase
• Third stage – following expulsion of the foetus till the placenta and membranes are delivered.

The entire process of labour and vaginal birth takes an average of 13 hours in women giving birth for the first time, and 8 hours in women who have given birth before. However, the exact duration varies a great deal from one woman to another. 18 hours of first stage is considered ‘prolonged’, and 1.5-2 hours of second stage is considered ‘prolonged’.

Stage 1 – Cervical dilation

Stage one lasts from the initiation of labour until there is full dilation of the cervix. The cervix will become thinner (a process known as effacement) and stretches (dilation) as the baby’s head will descend and “engage” with the pelvis. This process of contractions, thinning and stretching is usually painful for the mother. First stage is generally the longest stage. In a woman who is having her first baby, this first stage takes on average 8 hours. In a woman who has had previous children, this stage will be shorter, and takes on average 4 hours.

The first stage is divided into two parts:

• The latent phase, which is defined as period between the start of labour up until the cervix is 4cm dilated. This latent phase tends to be slow, lasting an average of around 6 hours for a first baby, and 4 to 5 hours for women who have had babies before, though it may last up to 8 to 12 hours.
• The active phase is from 4cm of cervical dilation until the cervix is fully dilated (10cm). During the active phase, it is expected that the cervix should dilate at least 1cm an hour in women who are having their first baby. The cervix in women who have had a previous vaginal birth tends to dilate more quickly (about 2cm/hr). During the first stage of labour, the midwife or doctor will regularly do a vaginal examination to assess how dilated the cervix is, how the baby is descending, and the colour of the amniotic fluid. This is done at least every four hours, or more regularly if necessary. The descent of the foetus through the birth canal is also tracked by examining the abdomen. The baby is monitored either intermittently or continuously using a CTG for signs of distress.

Stage 2 – Expulsion

This is from the time of full dilatation of the cervix until the baby is delivered. During this stage there are two phases:

• The initial part is a passive (descent) phase; where the baby’s head moves down through the mother’s vagina.
• This is followed by an active phase where the mother feels the desire to push.

This urge to push is usually less strong if the woman has an epidural. The pushing involves contracting the abdominal muscles in time with each uterine contraction. Pushing usually comes instinctively so there is no need to worry about “not knowing how to push”, however, it is important to push in time with uterine contractions to maximise efficiency and minimise fatigue.

In a woman who has had children previously, this active “pushing” phase takes on average 20 mins. In a woman who is having her first baby, the active phase takes an average of 40 mins.

Once the baby is delivered, the umbilical cord will be clamped and cut by the midwife/doctor. The stump shrivels up in a few days to form the belly button. The baby is then free to be held by the mother.

Breastfeeding soon after delivery is often encouraged as this may assist with the third stage of delivery and is beneficial to the baby.

Stage 3 – Delivery of the placenta

The third stage lasts from the delivery of the baby till delivery of the placenta and membranes (afterbirth). Third stage may be:

• Active: the doctor or midwife gives a drug (oxytocin) via an injection into the mother’s thigh just as the baby’s head is crowning (widest part coming through the vaginal opening) to help the uterus contract down to speed up delivery of the placenta, and they gently pull on the cord of the placenta to help deliver it. Active management of third stage is faster (around 5-10 minutes) and has been shown to reduce blood loss after delivery, so many hospitals prefer to use this method; or
• Physiological: No drugs or pulling on the placenta. The placenta delivers without assistance, or with gentle pushing from the mother. This takes a bit longer than active third stage (up to 30 minutes).

After the placenta is expelled, continued contractions of the uterus constrict the uterine blood vessels. This prevents extensive blood loss. Most women will lose some blood during the delivery process – this is expected. When there are larger volumes of blood lost, a midwife or doctor may need to manage this (see Post Partum Haemorrhage).

 

More information

For information on birthing statistics,various birthing types and other information related to giving birth, see Birth.

 

 

References

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2. Enkin M et al. A guide to effective care in pregnancy and childbirth. 4^th ed.Oxford: Oxford University Press; 2000.
3. Sweet B, Tiran D. Mayes Midwifery: A textbook for midwives. 13^th ed. Bailliere Tindall; Oxford: 1997.
4. Impey L. Obstetrics and Gynaecology 2^nd ed. Blackwell Publishing Ltd: Massachusetts; 2004.
5. Sherwood LS. Human physiology – from cells to systems. 5^th ed. Belmont: Brooks/Cole – Thomson Learning; 2004.