Induction and augmentation of labour

Induction of labour and augmentation of labour are performed for different indications but the methods are the same.

• Induction of labour: stimulating the uterus to begin labour.

• Augmentation of labour: stimulating the uterus during labour to increase the frequency, duration and strength of contractions.

A good labour pattern is established when there are three contractions in 10 minutes, each lasting more than 40 seconds.

If the membranes are intact, it is recommended practice in both induction and augmentation of labour to first perform artificial rupture of membranes (ARM). In some cases, this is all that is needed to induce labour. Membrane rupture, whether spontaneous or artificial, often sets off the following chain of events:

- Amniotic fluid is expelled;

- Uterine volume is decreased;

- Prostaglandins are produced, stimulating labour;

- Uterine contractions begin (if the woman is not in labour) or become stronger (if she is already in labour).

ARTIFICIAL RUPTURE OF MEMBRANES

• Review for indications.

Note: In areas of high HIV prevalence it is prudent to leave the membranes intact for as long as possible to reduce perinatal transmission of HIV.

• Listen to and note the fetal heart rate.

• Ask the woman to lie on her back with her legs bent, feet together and knees apart.

• Wearing high-level disinfected gloves, use one hand to examine the cervix and note the consistency, position, effacement and dilatation.

• Use the other hand to insert an amniotic hook or a Kocher clamp into the vagina.

• Guide the clamp or hook towards the membranes along the fingers in the vagina.

• Place two fingers against the membranes and gently rupture the membranes with the instrument in the other hand. Allow the amniotic fluid to drain slowly around the fingers.

• Note the colour of the fluid (clear, greenish, bloody). If thick meconium is present, suspect fetal distress.

• After ARM, listen to the fetal heart rate during and after a contraction. If the fetal heart rate is abnormal (less than 100 or more than 180 beats per minute), suspect fetal distress.

• If delivery is not anticipated within 18 hours, give prophylactic antibiotics in order to help reduce Group B streptococcus infection in the neonate:

- penicillin G 2 million units IV;

- OR ampicillin 2 g IV, every 6 hours until delivery;

- If there are no signs of infection after delivery, discontinue antibiotics.

• If good labour is not established 1 hour after ARM, begin oxytocin infusion. 

• If labour is induced because of severe maternal disease (e.g. sepsis or eclampsia), begin oxytocin infusion at the same time as ARM.

INDUCTION OF LABOUR

ASSESSMENT OF THE CERVIX

The success of induction of labour is related to the condition of the cervix at the start of induction. To assess the condition of the cervix, a cervical exam is performed and a score is assigned based on the criteria in Table P-6:

• If the cervix is favourable (has a score of 6 or more), labour is usually successfully induced with oxytocin alone.

• If the cervix is unfavourable (has a score of 5 or less), ripen the cervix using prostaglandins or a Foley catheter before induction.

TABLE P-6 Assessment of cervix for induction of labour 

OXYTOCIN

Use oxytocin with great caution as fetal distress can occur from hyperstimulation and, rarely, uterine rupture can occur. Multiparous women are at higher risk for uterine rupture.

Carefully observe women receiving oxytocin. 

The effective dose of oxytocin varies greatly between women. Cautiously administer oxytocin in IV fluids (dextrose or normal saline), gradually increasing the rate of infusion until good labour is established (three contractions in 10 minutes, each lasting more than 40 seconds). Maintain this rate until delivery. The uterus should relax between contractions.

When oxytocin infusion results in a good labour pattern, maintain the same rate until delivery. 

• Monitor the woman’s pulse, blood pressure and contractions and check the fetal heart rate.

• Review for indications.

Be sure induction is indicated, as failed induction is usually followed by caesarean section. 

• Ensure that the woman is on her left side.

• Record the following observations on a partograph every 30 minutes:

- rate of infusion of oxytocin (see below);

Note: Changes in arm position may alter the flow rate;

- duration and frequency of contractions;

- fetal heart rate. Listen every 30 minutes, always immediately after a contraction. If the fetal heart rate is less than 100 beats per minute, stop the infusion.

Women receiving oxytocin should never be left alone. 

• Infuse oxytocin 2.5 units in 500 mL of dextrose (or normal saline) at 10 drops per minute (Table P-7 and Table P-8 ). This is approximately 2.5 mIU per minute.

• Increase the infusion rate by 10 drops per minute every 30 minutes until a good contraction pattern is established (contractions lasting more than 40 seconds and occurring three times in 10 minutes). 

• Maintain this rate until delivery is completed.

• If hyperstimulation occurs (any contraction lasts longer than 60 seconds), or if there are more than four contractions in 10 minutes, stop the infusion and relax the uterus using tocolytics:

- terbutaline 250 mcg IV slowly over 5 minutes;

- OR salbutamol 10 mg in 1 L IV fluids (normal saline or Ringer’s lactate) at 10 drops per minute.

• If there are not three contractions in 10 minutes, each lasting more than 40 seconds with the infusion rate at 60 drops per minute:

- Increase the oxytocin concentration to 5 units in 500 mL of dextrose (or normal saline) and adjust the infusion rate to 30 drops per minute (15 mIU per minute);

- Increase the infusion rate by 10 drops per minute every 30 minutes until a satisfactory contraction pattern is established or the maximum rate of 60 drops per minute is reached. 

• If labour still has not been established using the higher concentration of oxytocin:

- In multigravida and in women with previous caesarean scars, induction has failed; deliver by caesarean section;

- In primigravida, infuse oxytocin at a higher concentration (rapid escalation, Table P-8):

- Infuse oxytocin 10 units in 500 mL dextrose (or normal saline) at 30 drops per minute;

- Increase infusion rate by 10 drops per minute every 30 minutes until good contractions are established;

- If good contractions are not established at 60 drops per minute (60 mIU per minute), deliver by caesarean section.

Do not use oxytocin 10 units in 500 mL (i.e. 20 mIU/mL) in multigravida and women with previous caesarean section. 

TABLE P-7

Oxytocin infusion rates for induction of labour (Note 1 mL = approximately  20 drops) 

Increase the rate of oxytocin infusion only to the point where good labour is established and then maintain infusion at that rate. 

TABLE P-8

 Rapid escalation for primigravida: Oxytocin infusion rates for induction of labour (Note 1 mL = approximately 20 drops)

PROSTAGLANDINS

Prostaglandins are highly effective in ripening the cervix during induction of labour.

• Check the woman’s pulse, blood pressure and contractions and check the fetal heart rate. Record findings on a partograph.

• Review for indications.

• Prostaglandin E2 (PGE2) is available in several forms (3 mg pessary or 2-3 mg gel). The prostaglandin is placed high in the posterior fornix of the vagina and may be repeated after 6 hours if required.

Monitor uterine contractions and fetal heart rate of all women undergoing induction of labour with prostaglandins. 

• Discontinue use of prostaglandins and begin oxytocin infusion if:

- membranes rupture;

- cervical ripening has been achieved;

- good labour has been established; 

- OR 12 hours have passed.

MISOPROSTOL

• Use misoprostol to ripen the cervix only in highly selected situations such as:

- severe pre-eclampsia or eclampsia when the cervix is unfavourable and safe caesarean section is not immediately available or the baby is too premature to survive;

- fetal death in-utero if the woman has not gone into spontaneous labour after 4 weeks and platelets are decreasing. 

• Place misoprostol 25 mcg in the posterior fornix of the vagina. Repeat after 6 hours, if required;

• If there is no response after two doses of 25 mcg, increase to 50 mcg every 6 hours;

• Do not use more than 50 mcg at a time and do not exceed four doses (200 mcg).

Do not use oxytocin within 8 hours of using misoprostol. Monitor uterine contractions and fetal heart rate. 

FOLEY CATHETER

The Foley catheter is an effective alternative to prostaglandins for cervical ripening and labour induction. It should, however, be avoided in women with obvious cervicitis or vaginitis.

If there is a history of bleeding or ruptured membranes or obvious vaginal infection, do not use a Foley catheter. 

• Review for indications.

• Gently insert a high-level disinfected speculum into the vagina.

• Hold the catheter with a high-level disinfected forceps and gently introduce it through the cervix. Ensure that the inflatable bulb of the catheter is beyond the internal os.

• Inflate the bulb with 10 mL of water.

• Coil the rest of the catheter and place in the vagina.

• Leave the catheter inside until contractions begin, or for at least 12 hours.

• Deflate the bulb before removing the catheter and then proceed with oxytocin.

AUGMENTATION OF LABOUR WITH OXYTOCIN

• Review for indications.

• Infuse oxytocin as described for induction of labour. 

Note: Do not use rapid escalation for augmentation of labour.

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