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 active phase of labour, with arrest for more than 4 hours, due to inadequate uterine contractions. 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 unscarred 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 indication.

7.4.4 Situations requiring special precautions

– Prior single low transverse caesarean section.
– Grand multiparity (5 deliveries or more).
– Overdistended uterus.

These factors increase the risk of uterine rupture. Oxytocin may be used provided the following precautions are respected:
1. maximum infusion rate of 30 drops/minute for 5 IU in 500 ml (i.e. 15 milli-units per minute);
2. assess maternal and foetal status before every dosage increase;
3. interval of at least 30 minutes between dose increases;

4. do not increase dosage (possibly even decrease dosage) if satisfactory uterine contractions and progress of cervical dilation. 

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 the event 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

Before administration

Technique

Monitoring during administration

During labour

Labour induction

• On vaginal exam, assess cervical dilation and effacement, and engagement (Bishop score ≥ 6, Table 7.1).
• 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 to obtain a solution of 10 milliunits per ml.
  • Start at 5 drops/minute, then increase by 5 drops/minute every 30 minutes, until contractions are effective (3 to 4 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 neonate 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 12 hours: stop the infusion and consider caesarean section.

Correction of dynamic dystocia

• Cervix at least 5 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: by 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 (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 (max. 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 IV infusion over 2 hours of 20 IU in 1 litre of Ringer lactate or 0.9% sodium chloride (160 drops/minute).

Uterine retraction.

Prevention of postpartum haemorrhage

Verify that there is no second twin.

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