7.4 The use of oxytocin during labour

7.4.1 Indications

– Induction of labour.
– Correction of a dynamic dystocia: delayed dilation in a woman in labour, with arrest for more than 2 hours, due to inadequate uterine contractions. The cervix must be dilated more than 3 to 4 cm, and effacement in progress. The membranes must have been ruptured.
– Contractions fail to resume 15 minutes after the birth of a first twin.

7.4.2 Risks of using oxytocin during labour

– Maternal risk: uterine rupture, especially in a scarred uterus, but in a sound uterus as well, particularly if it is overdistended (multiparity, polyhydramnios, multiple pregnancy) or if there is major foeto-pelvic disproportion.
– Foetal risk: foetal distress due to uterine hypertony (uterine contraction without relaxation).

7.4.3 Contra-indications to the use of oxytocin during labour

– Obvious foeto-pelvic disproportion, including malpresentation (brow, transverse, etc.).
– Complete placenta praevia.
– Spontaneous uterine hypertony.
– Foetal distress.
– Two or more prior caesarean sections.
– Prior classical caesarean section (vertical uterine incision).
– Absence of medical indication.

7.4.4 Situations requiring special precautions

– Prior single low transverse caesarean section.
– Grand multiparity.
– Overdistended uterus.

Oxytocin may be used to correct a dynamic dystocia during labour, provided the following conditions are respected:
1. maximum infusion rate of 30 drops/minute for 5 IU in 500 ml;
2. interval of at least 30 minutes between dose increases.

7.4.5 Conditions for oxytocin use

– Given the risk to both mother and foetus, use of oxytocin during labour requires:
• close maternal monitoring (check for hyperstimulation, dystocia and imminent rupture at least every 30 minutes);
• close foetal monitoring (check for decelerations in heart rate at least every 30 minutes);
• proximity to an operating theatre, in order to perform prompt caesarean section if needed.

– Position the patient on her left side.

In case of foetal distress, uterine hyperkinesia (more than 5 contractions in 10 minutes) or uterine hypertony (absence of uterine relaxation): stop the oxytocin.

After delivery, however, there is no risk of uterine rupture or foetal distress, and oxytocin can be used more readily.

Table 7.2 - Use of oxytocin

Indications

Precautions before administration

Technique

Monitoring during administration

During labour

Labour induction

• On vaginal exam, assess cervical dilation and effacement, and engagement.
• The harder and more closed the cervix and the higher the station, the harder induction will be.
• Verify the absence of foetal distress.

  • Dilute 5 IU in 500 ml or 10 IU in 1 litre of Ringer lactate or 0.9% sodium chloride.
  • Start at 5 to 8 drops/minute, then increase by 5 to 8 drops/minute every 30 minutes, until contractions are effective (3 contractions of more than 40 seconds in 10 minutes).
    On average, 20 drops/minute results in satisfactory uterine contractions. Do not exceed 60 drops/minute.
  • Once the infant has delivered:
    • use the existing IV line to administer the appropriate dose of oxytocin for prevention of postpartum haemorrhage;
    • let the current infusion finish.

• Appearance and quality of contractions, uterine relaxation.
• Foetal heart rate.
• General condition of the mother.
• Cervical dilation.

Rupture the membranes as soon as possible.
If the woman has not gone into labour after 8 hours: stop the infusion and start again the next day, if delivery is not urgent.

Correction of dynamic dystocia

• Cervix at least 3-4 cm on vaginal exam.
• Spontaneous or artificial rupture of membranes.
• No foeto-pelvic disproportion.

As for labour induction.

• Resumption or augmentation of contractions, uterine relaxation.
• Foetal heart rate.
• General condition of the mother.
• Cervical dilation.

No contractions 15 minutes after the birth of first twin

• Verify that presentation is vertical (not transverse).

• Start or resume oxytocin infusion.
• As for labour induction, but increase more rapidly: 5 drops every 5 minutes.

• Resumption or augmentation of contractions, uterine relaxation.
• Foetal heart rate.

Note: outside of labour, oxytocin is use as below

Haemorrhage due to uterine atony

• First, manually remove the placenta, if needed.
Routine uterine exploration.

IV infusion over 2 hours of 20 IU in 1 litre of Ringer lactate or 0.9% sodium chloride at a rate of 160 drops/minute. At the same time, give 5 to 10 IU by slow IV injection; repeat if necessary until the uterus becomes firm and contracted; do not exceed 60 IU total dose.

• Heart rate, blood pressure, blood loss.
• Uterine retraction.

After caesarean section


10 IU by slow IV injection after clamping the cord then 20 IU by IV infusion in 1 litre of Ringer lactate or 0.9% sodium chloride over 2 hours at a rate of 160 drops/minute.

• Uterine retraction.

Prevention of post-partum haemorrhage

• Verify that there is no 2nd twin.

5 to 10 IU by slow IV or IM injection, before or after the 3rd stage, depending on staff expertise.