Induction and augmentation of labour

Chapter 15 Induction and augmentation of labour



David T Y. Liu, Mentors: Sam Mukhopadhyay, Sabaratnam Arulkumaran



CHAPTER CONTANTS


Induction of labour as therapy 117

Indications for induction 117
Maternal 117

Fetal 117

Fetus and mother 118

Induction of labour as prophylaxis 118

Induction: general considerations 118

Contraindications to induction 118

Requirements before induction of labour 118

Induction of labour: process 119
Cervical ripening 119

Induction of labour 119

Bishop’s score of 4 or less 119

Bishop’s score between 4 and 7 (favourable cervix) 119

Induction of labour: artificial rupture of membranes 120

Technique for low ARM (forewater rupture) 120

Infusion of synthetic oxytocin (Syntocinon) 121

Risks of induction 121

Induction of labour: special situations 122
Previous caesarean section 122

Pre-labour rupture of membranes 123
For term fetus (36 completed weeks) 123

For 34 weeks’ gestation to term 123

Before 34 weeks’ of gestation 123

Breech presentation 123

Twin pregnancies 123

Intrauterine fetal death 123

Key points in induction of labour 124

Augmentation of labour 124
Augmentation before 3 cm cervical dilatation 124

Augmentation after 3 cm cervical dilatation 124

Induction of labour is a process for initiation of uterine activity to achieve vaginal delivery. Induction rates between 10% and 25% reflects current policies, referral patterns and sometimes women’s choice. Labour is initiated to benefit principally the mother, the fetus or both and as an elective prophylactic procedure. In the UK, women with uncomplicated pregnancies are offered induction of labour after 41 weeks.



INDUCTION OF LABOUR AS THERAPY


This is considered for the following reason:


• When it is safer for the woman not to continue pregnancy. Consider the woman’s preferences and priorities.

• When the fetus is less at risk if delivered or when both mother and fetus benefit by delivery. Induction must be the most appropriate mode of delivery.

Close surveillance in labour is mandatory when induction is carried out to address fetal or maternal compromise. If fetal distress develops or labour is not progressing well early resort to caesarean section is advised.



INDICATIONS FOR INDUCTION



Maternal


Medical or obstetric conditions not responding to treatment and which threaten the woman’s health, such as heart failure, severe pre-eclamptic toxaemia and deteriorating renal function or central nervous system disorders.



Fetal


Presence of progressive growth restriction, abnormality not compatible with life, or fetal death.



Fetus and mother


Where induction of labour benefits both the mother and fetus, such as in poorly controlled diabetes, following rupture of fetal membranes or when chorio-amnionitis is evident. This indication is particularly pertinent in contemporary obstetric practice when women with medical conditions previously not considered suitable for pregnancy are now prepared to accept inherent risks to become mothers.



INDUCTION OF LABOUR AS PROPHYLAXIS


Induction of labour is also considered to anticipate potential complications. Examples are:


• Even in uncomplicated pregnancies, evidence suggests the fetus is best delivered by 2 weeks post term. Prophylactic induction reduces the incidence of caesarean section, instrumental delivery, fetal compromise during labour and perinatal mortality.

• To achieve better control after previous precipitated labour. (Labour less than 2 hours.)

• To avoid fetal demise in prior unexplained sudden death after fetal maturity.

• To avoid macrosomia and complications of shoulder dystocia especially in a diabetic woman.

• Occasionally induction is considered for logistic or psychosocial reasons such as difficult access to hospital because of distance.


INDUCTION: GENERAL CONSIDERATIONS



• Before formal induction, current practice suggests women should be offered membrane sweeping.

• Labour can subject both mother and fetus to stress. If there is significant compromise consider caesarean section as the preferred mode of delivery.

• When advice for induction of labour is declined close fetal and/or maternal surveillance is essential, e.g. scan for liquor volume, twice weekly cardiotocograph (CTG).

• When induction for fetal or maternal compromise fails deliver by caesarean section. When failure follows prophylactic indications, there is the option to reassess and repeat the process.


CONTRAINDICATIONS TO INDUCTION


Induction of labour should not be considered in the following situations:


• When vaginal delivery is not advised or possible, for example pelvic disproportion, placental praevia, cord presentation and in the presence of active infection such as genital herpes.

• Uterine contractions can cause uterine rupture after previous classic or inverted T uterine incision, after myomectomy or surgery which extends into the uterine cavity and where lower segment caesarean section is complicated by extension or infection. Review operation notes from previous caesarean sections. Palpate to exclude tenderness over previous lower segment caesarean section scar.

• Induction is contraindicated if labour threatens further compromise for mother and/or fetus.

Only proceed when the woman provides informed consent.



REQUIREMENTS BEFORE INDUCTION OF LABOUR


Review medical and obstetric history. Perform clinical examination to exclude contraindications for induction of labour. Ensure the woman and her partner are fully informed of the risk and benefits and consent to the intended programme. Provide written information.


Perform vaginal examination to assess adequacy of pelvis and determine cervical status. Cervical dilatation, cervical length, consistency, position and station of presenting part are combined into a score – Bishop’s score (Table 15.1), often modified to describe cervical status (Figure 15.1). A low score forewarns increased likelihood of induction failure and need for cervical preparation or ripening.



Table 15.1 Modified Bishop’s score

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Figure 15.1 Cross-section of cervix to illustrate the degree of effacement.


Cervical dilatation exerts twice the influence on successful induction compared with cervical consistency.



INDUCTION OF LABOUR: PROCESS


Cervical status governs choice for methods to induce labour. A low or unfavourable cervical score necessitates a ripening process for effacement and/or softening of the cervix to facilitate cervical dilatation. This is achieved by drugs, for example prostaglandins, which soften the cervix and produce uterine activity to draw up or create cervical effacement. Membrane sweeping releases prostaglandins and provides a biomechanical advantage to initiate or assist induction.



Cervical ripening


Pharmacological substances such as prostaglandins are prescribed to prepare or ripen the cervix. The current most clinically acceptable and effective is prostaglandin E2 (PGE2). PGE2 given intravaginally as a pessary, as water soluble gel or more recently in the form of a slow-released hydrogel is associated with least systemic side effects. Vaginal pH, moisture, temperature, and infection can, however, all affect efficacy of the preparation. Do not use obstetric cream for vaginal examination if prostaglandins may be given. Where appropriate membrane sweep is returning as an acceptable procedure for uncomplicated pregnancies over 40 weeks. Both vaginal gel and vaginal tablets are equally effective and use is governed by cost.



Induction of labour


Auscultate fetal heart and perform CTG trace for 30 minutes prior to the induction process. Omit if induction is for fetal demise. If the trace is non-reassuring, discuss delivering by caesarean section.



Bishop’s score of 4 or less


Administer 2 mg prostaglandin gel into posterior fornix. Give another 1 mg in 6 hours if needed. Review by experienced obstetrician 6 hours after second dose. Uterine activity usually starts 1 hour after administration of prostaglandin gel. Pharmacological effect lasts up to 4 hours. Continuous CTG monitoring is essential. When there is no urgency let the woman rest overnight and recommence the programme in the morning. The maximum total dose of PGE2used is 4 mg for primigravidae and 3 mg for multigravidae. Vaginal prostaglandin tablets are alternatives (3 mg PGE2 vaginally and repeat once in 6 hours). With ruptured membranes consider vaginal prostaglandin or intravenous oxytocin.

Related posts:

  1. Maternal and perinatal mortality
  2. Obstetric emergencies: training with skills drills
  3. Episiotomy and tears
  4. Assisted vaginal delivery and shoulder dystocia

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Mar 16, 2017 | Posted by in NURSING | Comments Off on Induction and augmentation of labour

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