7.4 The use of oxytocin during labour

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    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.