Open access peer-reviewed chapter - ONLINE FIRST

Induction of Labour

Written By

Benjamin Joseph Nggada

Submitted: February 21st, 2022 Reviewed: March 10th, 2022 Published: April 29th, 2022

DOI: 10.5772/intechopen.104445

IntechOpen
Childbirth Edited by Julio Elito Jr.

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Childbirth [Working Title]

Prof. Julio Elito Jr.

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Abstract

Induction of labour is one of the common obstetric interventions in the world with varied incidence rates between developed and developing countries. It is generally employed by obstetricians and physicians managing pregnant women when the risk of continuing such pregnancy is far greater than delivery at that said point. A detailed evaluation and indications for induction of labour should be done for every single woman. Methods of induction of labour could be pharmacological, mechanical or both; taking care to reduce or eliminate complications associated with this intervention. Decision for induction of labour should involve the most senior member of the team with a woman centered approach to care. Induction of labour carries multiple risks and complications compared with spontaneous onset of uterine contractions with increase tendency of operative vaginal delivery and caesarean section.

Keywords

  • pre-inductive cervical state
  • induction of labour
  • onset of labour
  • postdate
  • augmentation
  • misoprostol

1. Introduction

Induction of Labour (IOL) is one of the common obstetric procedures and or intervention encountered in maternity unit(s) all over the world [1]. Usually, the risk of continued pregnancy is far more detrimental to the mother or her unborn baby or both [1, 2]. Therefore, a balance in favour delivery is anticipated and planned with the anticipating mother using a woman centered approach [3, 4]. Decision for induction of labour should be led by the most experienced obstetrician on ground in consultation with the team managing such pregnancy. IOL will set up a cascade of events cumulating to the delivery of the baby and automatically elevates that pregnancy state to high risk [2]. These processes are important that they are closely monitored to end point and beyond.

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2. Epidemiology

The incidence of induction of labour varies between different settings and appears to be on the rise especially in developed countries. In the United States the rate of IOL is quoted to be approximately 30 percent [5]. While in the United Kingdom (UK) the recent maternity figures show an increase rate of 2.1% from the 29.4% in 2016–2017 to 31.6% in 2017–2018 [6] according to the Hospital Episode Statistics. This increase in induction rates in developed countries and particularly in the UK is attributed to improved diagnostic tools and better understanding of maternal medicine, advanced maternal age, and socioeconomic class variation [7, 8, 9]. The incidence of induction in Africa has been found to be below 10 percent in most settings. In a recent cross-sectional study to assess the prevalence, outcome and associated factors among women delivered at public hospitals in Ethiopia, Lueth et al. [10] reported a prevalence of 9% and failed IOL was responsible for 3.3% increase in caesarean section rates. Vogel et al. [11] in a secondary analysis of data for World Health Organization (WHO) global survey on maternal and neonatal health found that the unmet needs of IOL were between 60% and 80% with an average rate of IOL of 4.4%. In resource-constrained settings there is less capacity due to inadequate facilities, lack of trained staff and limited centers where safe caesarean sections can be performed on a 24 h basis.

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3. Definition of terms

In order to understand the concept of induction of labour, some key terms need to be clearly understood:

Induction of Labour (IOL):This refers to the artificial initiation of uterine contractions before their spontaneous onset at or beyond the age of viability with the sole aim of delivery of the fetoplacental unit where the benefit of pregnancy termination exceeds its prolongation [1, 2, 7, 10, 11].

Successful IOL:Is said to occur when vaginal delivery is achieved usually within 24–48 h [12].

Failed IOL:In recent National Institute for Health and Care Excellence (NICE) guideline, unsuccessful IOL is considered when once cycle of treatment has failed to initiate uterine contractions [13]. Some authors refer to failed induction as the inability to achieved adequate uterine contractions after 6–8 h of oxytocin administration and at ceiling doses for at least an hour [14]. It is important to understand that failed IOL should not always results in emergency caesarean section as studies have shown that considerable number of women will delivery beyond such set points [15].

Cervical ripening:Is the change of cervical physical and chemical (intrinsic) morphology as a result of realignment of collagen fibres and extracellular matrix from firm to a compliant structure with gradual softening, effacement and dilatation which increases the likelihood of vaginal delivery. It can be from a natural process, chemically or mechanically induced [12, 13, 16].

Tachysystole:Is said to occur when there are greater than 5 contractions in 10 min in a period of approximately 30 min. Uterine tachysystole is further subdivided into two categories: with or without fetal heart rate changes [13, 17, 18, 19]. This could be spontaneous or induced.

Hypertonus:When uterine contractions duration is more than 2 min without fetal heart rate changes. This is also considered as increase in uterine tonus, which is intrauterine pressure between contractions [13, 19].

Hyperstimulation:Refers to tachysystole or hypertonus with abnormal fetal heart rate changes. This term is largely abandoned, and it is replaced with tachysystole with fetal heart abnormalities. [13, 18].

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4. Understanding onset of labour

Labour diagnosis is one of the most important clinical judgements in maternity care and is much more important to understand its onset. However, the mechanisms involved in the onset of labour still remains blurred and why some women will reach postdate or post term without spontaneous onset of labour is elusive. Our narrow understanding of the mechanism of onset of labour makes IOL difficult [19]. Usually, a cascade of biochemical events heralds the onset of a complex well-regulated process that results in cervical ripening, occasional membrane rupture and high frequency myometrial contraction that result in the expulsion of the fetoplacental unit [20].

The mechanism of spontaneous onset of labour has a fetal, placental/fetal membranes and maternal components that contribute to its onset via series of paracrine/autocrine hormones. Uterine quiescence that is maintained throughout pregnancy is switched off by the withdrawal of the functional inhibitory effect of progesterone via progesterone receptor (PR). There is an increase unbalance ratio of progesterone receptor key isoforms with more expression of progesterone receptor A (PR-A) compared with progesterone receptor B (PR-B) that increases with advancing gestational age and might also inhibit the PR-B genes. The overwhelming increased ratio of PR-A to PR-B may promote transcription of contractile protein CX43 [20, 21] and increase gap junctions’ formation in the myometrium [22]. Oxytocin receptors (OXTR) gradually increase with advancing gestational age which may directly increase intracellular calcium concentrations [23].

Prostaglandins (PG) play major roles in initiation and maintenance of uterine contraction via prostaglandin receptors. The prostaglandins that play major role in inducing myometrial contractility are prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) which induces intracellular calcium by opening calcium gated channels. Spontaneous labour is also associated with sterile inflammation with increase infiltration of leucocytes and upregulation of inflammatory cytokines and chemokines, particularly interleukin 1B which increases expression of calcium transport protein. Though there are plethora of literatures toward the physiology of the onset of labour, its exact pathway remains elusive [20, 21, 22, 23].

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5. Indications and contraindications of IOL

The indication(s) for induction of labour should be weighed on the scale of clinical judgement to ascertain that the benefit(s) of delivery outweighs continuation or prolongation of such pregnancy. This decision should be taken seriously, and there should be shared decision between the managing clinicians and the woman as well as appropriate informed consent taken. Prior to informed consent there should be a dialogue on the primary indication for IOL and other contributory factors, risks and benefits, methods and rationale, and realistic expectations [24].

Indications [13, 25]Contraindications [13, 25] ] confirmed
Post term >42 weeks
Late term pregnancy/postdate 41 0–41 6 weeks
Preeclampsia >37 weeks
Eclampsia
Chronic hypertension
Gestational hypertension >38 weeks
Twin gestation
• Uncomplicated dichorionic twin pregnancy > 38 weeks
• Uncomplicated monochorionic twin pregnancy > 36/37 weeks
Diabetes in pregnancy or gestational diabetes
Alloimmune disease near term or at term
IUGR
IUFD
Intrahepatic cholestasis of pregnancy
Prelabour rupture of membrane at term or near term
Preterm Prelabour rupture of membrane with GBS colonisation
Oligohydramnios
Chorioamnionitis
Significant but stable antepartum haemorrhage
Obstetric Cholestasis
Maternal refusal
Prior classical, De Lee or inverted T incision
Significant prior uterine surgery (e.g. full thickness myomectomy)
Previous hysterotomy
Two or more previous caesarean sections
Previous uterine rupture
Fetal malpresentation (e.g. transverse lie, footling breech)
Placenta previa
Vasa previa
Cord presentation
Active genital herpes
Invasive cervical cancer
Controversial
Prior IUFD
Care giver or maternal request
Suspected fetal macrosomia
One previous caesarean section
Previous vesicovaginal fistula
Previous OASIS

Table 1.

Indication for induction of labour (Table 1).

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6. Preinduction cervical state

The Bishop’s score is used to assess the pre-inductive state of the cervix and to forecast the favorability of the cervix to comply during IOL. IOL is highly likely to fail if it is embarked upon without a proper assessment of the woman and consideration of the bishop score. The cervix retains its firm rigidity throughout pregnancy. As the uterus enlarges, the cervix becomes softer and distensible in preparation for labour and delivery by ripening. Ripening is a complex series of biochemical processes that results in softening of the cervix, effacement, and dilation. This usually occurs prior to uterine contractions for both spontaneous and iatrogenic labour. The cervix is composed of fibroid connective tissue, collagen (type I, III predominately and a small amount of type IV), elastin, vasculature, fibroblast, and smooth muscle [25, 26].

Cervical remodelling is associated with increase vascularity, stromal and glandular hypertrophy. There is concomitant increase in inflammatory activities with production of cytokines which leads to the release of metalloproteases (2 and 9) that degrades cervical collagens. The extracellular matrix which is strengthened by proteoglycans is gradually reduced with an unbalanced increase in glycosaminoglycans. The remodelling of the cervix is associated with decreased cross-linkages between collagen helices which cumulates to increased compliance to softening, effacement, and dilation [26].

Various hormones are responsible for this complex interaction that leads to cervical ripening. Increase in cyclooxygenase −2 lead to rise in the level of local PGE2 and PGF2α. PGE2 will activate a series of reactions: increase dilatation of small vessels in the cervix, increase collagen degradation, increase in hyaluronic acid, increase chemotaxis for leucocytes and increase release of Interleukin −8. PGF2α stimulate an increase in glycosaminoglycans. The role of Nitric Oxide (NO) has been the focus on recent studies on its contribution to cervical ripening. Increased levels of induced Nitric Oxide Synthase (iNOS) activity by resident and migrating inflammatory cells is associated with cervical ripening by dramatic increase in NO. NO might play a role by increased activities of metalloproteases [27, 28, 29].

Dr. Edward Bishop in 1964 proposed a Prelabour scoring system to assess the likelihood of going into spontaneous labour [30]. It has now undergone several modifications to assess the favourability prior to IOL. The score is an aggregate sum of the cervical dilatation, consistency, effacement, position and fetal station [31]. A total score of 6 and above is considered favourable and score below that is deemed unfavourable. The Calder Modification replaces cervical effacement with cervical length with a total score of 12 [31, 32]. In a retrospective study [33] done recently to closely look at the relationship between bishop score and successful induction, a higher bishop score (8–10) at the beginning of IOL is directly proportional to the higher rates of successful IOL compared with bishop score between 6 and 7. There is recent evidence to show that the cervical length assessment by transvaginal ultrasound appear to be superior to the bishop score, however this is not a routine practice [34].

Cervical featuresScore
0123
Cervical dilatation (cm)01–23–4>4
Length (cm)>43–41–2<1
Station of the presenting part (cm)−3−2−1/0+1/+2
ConsistencyFirmAverageSoft
PositionPosteriorMid/Anterior

Table 2.

Modified Bishop’s (Calder) score [31, 32] confirmed (Table 2).

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7. IOL check list

An induction check list is good clinical practice to ensure women are properly prepared, improve IOL success and prevent complications. Every maternity setting should have an IOL check list tailored to meet their local standard. A check list should have the patient’s biodata, informed consent, gestational age, indication for IOL, patient routine booking investigations, associated comorbidity, previous surgeries, and the bishop score. A recent ultrasound with estimated fetal weight - which also rules out any contraindication for vaginal delivery, an admission CTG and the method of cervical ripening and IOL with the responsible doctor’s name and signature should be clearly documented [35].

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8. Cervical ripening and IOL agents

Cervical ripening and induction agents can be group into pharmacological, mechanical and combination of both. While some agents are intended to ripen the cervix before initiation of induction of labour, majority will progress to initiate uterine contractions. See Table 3.

8.1 Prostaglandins

Prostaglandins have gained wide acceptance as a cervical ripening and induction agent over the decade and is now considered a preferred agent for both. However, they are said to be associated with a small risk for tachysystole and fetal heart rate changes [36]. Misoprostol—a synthetic prostaglandin E1 analogue—is heat stable and low cost compared to Dinoprostone. This has seen its wide usage especially in low resource setting. Misoprostol availability is said to bring equity in the disparity of induction of labour between developed and resource constrained regions of the world and recently a low dose misoprostol preparation was approved for IOL in Nordic countries [37, 38]. The dosing and timing of misoprostol ranges 25–50 mcg every 2–6 h. However, in a study of balancing efficacy and safety, the minimum efficacious dose associated with less complication is 25 mcg [38], while the vaginal compared with the oral route appears to offer significant clinical advantage in successful vaginal delivery [39].

Dinoprostone is prostaglandin E2 that comes in two popular preparations as Cervidil, a control release hydrogel suppository 10 mg vaginal inserted every 12 h at 0.3 mg/h. and Prepidil administered as an intracervical gel of 0.5 mg/2.5 ml or 1 or 2 mg for intravaginal insertion every 4–6 h with a maximum of 3 doses in 24 h. Dinoprostone needs to be refrigerated and is relatively expensive for resource constrained settings [40, 41]. The International Federation of Obstetrics and Gynaecology (FIGO) recently established an expanded chart on the dosage of misoprostol in variety of Obstetric and Gynaecologic conditions in the light of new evidence and through expert contributions which has been endorsed by FIGO safe motherhood and newborn health committee (Table 4) [42].

PharmacologicalMechanicalCombination
Prostaglandins
  • Prostaglandin E2 (Dinoprostone)

  • Prostaglandin E1 (Misoprostol)

Oxytocin
Transcervical catheters
  • Foley

  • Cook

Extra-amniotic saline infusion
Stripping membrane
Laminaria
Cervical hygroscopic dilators
Extra-amniotic saline infusion
Transcervical catheter + Prostaglandins
Transcervical catheter + Oxytocin

Table 3.

Cervical ripening and induction agents.

Table 4.

FIGO misoprostol-only recommended regimens 2017 [42] confirmed.

8.2 Oxytocin

Oxytocin is a neuropeptide hormone produced by the hypothalamus via the paraventricular nuclei and stored in the posterior pituitary gland. It is secreted when triggered by labour, lactation, social interaction, and stressors. Oxytocin acts on the myometrium to induce uterine contractions via G-proteins with the subsequent release of intracellular calcium stores through a complex interplay on its activity on phospholipase C. Its potency is directly proportional with advancing gestational age when there are sufficient oxytocin receptors [43]. The synthetic oxytocin is a cyclic nonapeptide which is identical to the natural oxytocin obtained via chemical synthesis. Oxytocin acts within a minute of intravenous injection and 2–4 min via the intramuscular route. In a low dose infusion, it causes rhythmic uterine contractions with a repetitive pattern. It can cause sustained uterine contraction at high dose infusion. It reaches its steady state between 20 and 40 min during continuous infusion, and it is metabolised and cleared by the liver and kidneys with about 1 percent unchanged in the urine [43, 44].

Oxytocin might have plausible synergistic effect in cervical ripening, however its role as a cervical ripening agent is not well established [45]. There are still controversies on its optimal regimen for induction of labour with varied protocols in different settings. However, a low dose regimen initiated between 0.5 and 1 mU, and increased by 1 mU/min every 30–40 min interval is preferred over high dose regimen of 4–6 mU [44].

Maternal and Child Health (Obstetrics and Gynaecology Division) University of Namibia

  1. Dosage

    The dose of oxytocin is calculated using the formula: 10 units of oxytocin in 1000 ml of normal saline or ringers’ lactate is equivalent to 10,000 mU. Therefore, each ml (1 ml) of fluid mix is 10 mU. In 1000 ml give 6 ml/h (60 mU/h.)

    Starting dose at 1 mU/min oxytocin infusion should be escalated at 30 min interval until adequate and strong contractions (3–4 lasting 40–50 s in 10 min) is established.

    The 2 IU in 200 ml is recommended because it is cost effective with less water intoxication in resource constrained settings. Oxytocin dose of greater than 20 mU/min highlighted in red is to be administered only by a senior resident doctor or a specialist. Low dose oxytocin infusion should be administered by infusion pump, however in settings where there are no infusion pumps, a senior doctor should closely monitor the infusion at a rate of 10 drops/min in a diluent of concentration of 10 IU in 1000 ml escalated every 30 min maximum of 60 drops/min.

  2. Preparation

    1. Obtain informed consent for oxytocin induction and or augmentation of labour

    2. Do a pre induction and or augmentation CTG before the onset of oxytocin

    3. Continuous CTG is advised for all patients

    4. Do haemoglobin and obtain blood for blood group and save serum

    5. Do not administer oxytocin on a previous uterine scar except by a specialist instruction (such specialist should monitor the patient)

    6. Clearly document the indication for oxytocin use in the labour care guide

    7. Inform all the managing/incoming team/theatre staff/Anaesthetist

    8. For induction of labour: use oxytocin only in patients with bishop score >6 and perform artificial rupture of membrane if the membranes are intact

    9. Do not give oxytocin within 6 h of prostaglandin use

  3. Monitoring

    1. Continuous CTG

    2. Escalate the dosage every 30 min after assessment of maternal condition, fetal condition, and uterine contraction

    3. Maintain, reduce, or stop dose when adequate uterine contractions are achieved (3–4 contractions in 10 min lasting 40–50 s)

    4. Use the labour care guide in monitoring all patients on oxytocin infusion

    5. STOP oxytocin and give plain normal saline whenever there is uterine hyperactivity:

      1. Tachysystole

      2. Hypertonus

      3. Hyperstimulation

        The woman should adopt a left lateral position.

        Consider supplemental oxygen, especially when there are signs of maternal hypoxia or category III CTG changes characterised by absent baseline variability with any of the following: recurrent late decelerations, recurrent variable decelerations, bradycardia, or sinusoidal pattern. Consider delivery if fetal heart rate abnormality persists.

    6. Fetal rate abnormality may be the earliest sign of uterine rupture especially in patients on oxytocin infusion

    7. After 4 h, stop infusion to reassess if there is any benefit of further infusion

8.3 Transcervical catheters

The transcervical extra-amniotic catheters have been one of the oldest methods of cervical ripening and induction of labour [46]. The Foley catheter has a single balloon with a capacity between 30 and 80 ml that is inserted into the extra-amniotic space compared to the more recent Cook’s catheter with double balloons with one inserted into the extra-amniotic space as the uterine balloon and another below the cervix as the vaginal balloon with capacity of 80 ml for both [47]. In a Cochrane data base of systematic review of 23 studies [48], there were no statistically significant difference in comparing Foley catheter and prostaglandins in achieving vaginal delivery within 24 h with similar incidence of caesarean section rates. However, the transcervical Foley’s catheter had lower incidence of tachysystole and or fetal heart rate abnormalities [48].

In a randomised controlled trial comparing a 30 and 80 ml Foley catheter balloon for preinduction cervical ripening, 80 ml provided faster labour, more dilatation and decrease need for oxytocin [49]. However, no significant difference was found between 12- and 24-h duration in induction delivery interval [46]. Other additives like applying traction and weight to the catheter has demonstrated faster expulsion of the Foley without any effect on the induction delivery interval (Figure 1) [50].

Figure 1.

Transcervical extra-amniotic Foley’s catheter [46].

A single transcervical Foley catheter without extra-amniotic saline has better patient satisfaction with less discomfort compared with the double balloon catheter and it is cost effective especially in resource constrained settings [51]. Recent evidence is suggesting that highly motivated women can use transcervical Foley balloon in an outpatient setting with no increase in morbidity and or adverse outcome [52].

One of the major concerns of transcervical balloon catheters is theoretical risk of infection. This risk has not been validated and the rates of puerperal and neonatal infection appear similar to other methods of induction [53, 54, 55].

Combination of mechanical and pharmacologic methods has been one of the recent advances in labour induction to increase efficiency and efficacy, reduce cost and reduce adverse effects of induction agents to the mother and her baby. The BIGIN trial was a randomised control trial that compared buccal versus vaginal misoprostol with Foley catheter. The vaginal misoprostol with Foley catheter resulted in a shorter induction delivery time with similar caesarean section rates, perinatal and maternal morbidity among both arms of the study. Therefore, vaginal misoprostol combination is recommended as the preferred method for combination method [56].

8.4 Stripping membrane

This is an old but reliable method of inducing cervical remodelling to comply with induction of labour. It is a mechanical method that involves a digital vaginal examination with the aim of placing one or two gloved fingers -usually the index and the middle - into the cervix and thereafter performing a circular sweeping motion. This is an artificial separation of the membrane that increases the activity of PGF2 and phospholipase which induces the complex cascade of cervical ripening [57]. In a recent Cochrane review [58], there is more likelihood to have spontaneous vaginal delivery among women who had their membranes swept. NICE guidelines on IOL recognised sweeping of membrane as an adjunct to formal induction [13]. Membrane sweeping can be offered to women from 39 weeks of gestation and thereafter additional membrane sweep could be offered at 40 and 41 weeks if there is no onset of spontaneous labour after the first membrane sweep [13]. There are concerns on the possibility of large doses of bacteria pushed above the internal os resulting in increased risk of maternal and fetal infection especially when there is a prolonged delay between membrane sweep and the onset of labour [57]. The role of cervical massage as an alternative method to membrane sweeping appears promising with significant effect on bishop score and can be considered as a reasonable option; especially if the cervical os is closed [59].

8.5 Laminaria and cervical hygroscopic dilators

Laminaria are dried seaweed stems (Laminaria japonica or Laminaria digitalis) that can be placed in the cervix to induce cervical ripening by absorbing water and expanding to cause cervical dilation and provoke endogenous prostaglandin release [60, 61]. Dilapan-S (MEDICEM, the Netherlands) is a sterile hygroscopic cervical dilator that has demonstrated no increased risk of infection like the laminaria tents. They are polymer rods which consist of the dilating part made of hydrogel and a polypropylene handle. An international observation study has revealed that Dilapan-S has not increased the risk of hyperstimulation and may be used in an outpatient setting [61, 62].

8.6 Artificial rupture of membranes (AROM)

Amniotomy can be used as an adjunct to induction of labour in a woman whose cervix is accessible and favourable. It is usually a prelude to oxytocin induction. However, in recent NICE guideline, it is not recommended as a sole method of induction with or without oxytocin except where prostaglandins are contraindicated [13, 61]. A recent randomised controlled trial has found that immediate oxytocin administration after AROM was not associated with shorter AROM to delivery time compared to delay of 4 h. Therefore, the decision to use any method should follow local protocols based on resources and maternal choice [63]. It is important to remember that there is a major risk of the cord prolapse with an unengaged presenting part.

Other methods of cervical ripening and induction of labour are yet to be clinically validated. Therefore, the use of mifepristone, acupuncture, homoeopathy, hypnotic relaxation, baths, enema, sexual intercourse, breast stimulation, intracervical hyaluronidase, relaxin, corticosteroids, and oestrogen need further research [64].

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9. IOL in special clinical scenarios

Certain obstetric conditions occur more commonly, therefore a brief overview of IOL in these conditions are highlighted.

9.1 Prolonged pregnancy

Prolonged pregnancy is a loose term that applies to all pregnancy beyond estimated due date which comprises of postdate and post term pregnancy. It occurs in about 5–10% of all pregnancy and the rate is reduced to incidence of 2–5% with ultrasound dating in the first trimester. A better classification of term pregnancy underscores the importance of late term (41 0/7–41 6/7 and post term (42 0/7 and beyond) on uteroplacental insufficiency with increase perinatal morbidity and mortality. The risk of still birth, macrosomia, shoulder dystocia, birth injury, postpartum haemorrhage and meconium aspiration syndrome are higher at late term and post term compared with early term (37 0/7–38 6/7) and full term (39 0/7–40 6/7) [13, 65]. Therefore, NICE guidelines and WHO recommends IOL at 41 weeks and beyond. In the rare circumstances when the woman declines IOL beyond 42 weeks, she should have twice weekly CTG and ultrasound and be counselled based on findings [1, 13]. Neonatal outcome did not improve following IOL at 39 weeks compared with expectant management in a multicenter trial (ARRIVE) in the United States, however the rate of caesarean section was lower in the intervention arm [66].

9.2 Hypertensive disorders of pregnancy

Hypertension complicates about 10% of pregnancies and remains one of the major causes of perinatal and maternal morbidity and mortality [67, 68]. Preeclampsia is considered a severe form of hypertension in pregnancy with an incidence of 2–5% of all hypertensions in pregnancy. Early onset (<34 weeks) and preterm preeclampsia (<37 weeks) could present with severe disease to prompt immediate delivery [68]. Following the HYPITAT Trial I, women with gestational hypertension or preeclampsia at term should be offered delivery. While HYPITAT II trial, recommends that non severe hypertension between 34 and 37 weeks should be delivered at 37 weeks [69, 70].

9.3 Prelabour rupture of membrane

The rupture of amniotic sac before the onset of labour is termed as prelabour rupture of membrane which can occur before (preterm prelabour rupture of membrane) or after 37 weeks of gestation (term prelabour rupture of membrane) [71]. Preterm (24/0–36/6) prelabour rupture of membrane (PPROM) complicates about 3% of pregnancies and is responsible for about 30–40% of preterm births. The Royal College of Obstetricians and Gynaecologists recommend conservative management for uncomplicated PPROM to 37 weeks. Prelabour rupture of membrane should be offered delivery after 37 weeks if it occurs and there is no onset of labour within 24 h or when PPROM is complicated by infection [72]. The induction method can either be by prostaglandin or oxytocin, however, the Bishop Score should be made favourable before such induction is embarked upon.

9.4 Hyperglycaemia in pregnancy

Hyperglycaemia is considered as one of the most common medical conditions in pregnancy with one in every 6 live births occurring in women with some degree of hyperglycaemia. Gestational Diabetes Mellitus is the most common type, and it is responsible for 84% of hyperglycaemia in pregnancy. There are higher incidences of perinatal and maternal morbidities and mortalities among pregnant women with any form of hyperglycaemia. A balance of glycaemic control and fetal maturity should be weighed to consider the timing of delivery. FIGO recommends delivery for women at 40–41 weeks for a well-controlled hyperglycaemia with fetal weight of <3800 g while delivery via induction is recommended at 38–39 weeks for poorly controlled hyperglycaemia with babies that are between 3800 and 4000 g. Elective caesarean section is the preferred delivery mode for babies weighing 4000 g and above [73].

9.5 IOL in previous caesarean section

The high rates of uterine rupture in patients with previous caesarean section is well established. There is a 2–3 times higher risk of uterine rupture in patient induced or augmented with previous caesarean section. This risk should be understood by both the physician preferably, a senior obstetrician, and the patient before undergoing induction or augmentation of labour in women with previous caesarean section. The risk of uterine rupture is lower with mechanical methods (Foley catheter and amniotomy) compared with prostaglandins [74].

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10. Augmentation of labour (AOL)

Improving the efficiency of uterine contractions by increasing the frequency, duration, and intensity in women with inadequate or uncoordinated uterine contractions of spontaneous onset to reduce or prevent adverse outcome for the babies and their mother associated with prolonged labour is best describe as augmentation [75, 76]. The term AOL is loosely applied to women undergoing induction of labour, but this is a misnomer because contractions in induction of labour are not of spontaneous onset. The decision to augment the labour process should be carefully and meticulously evaluated after a thorough history and examination excluding any cephalopelvic disproportion and establishing that the cause of unsatisfactory progress of cervical dilatation and descent of the presenting part is solely the problems of power. Every local maternity setting should have a protocol of AOL using oxytocin infusion which is usually the same strength and frequency with induction protocol (see Table 5). Low dose oxytocin regimen is favoured because of less complications related to augmentation [76]. AROM can be considered as a sole method AOL because it enhances uterine contractions by increasing plasma prostaglandins, however the effectiveness of AROM appears to be debatable [77, 78].

Oxytocin regimens
Time from start (min)Oxytocin dose (mU/min)Volume of infusion (ml/h)
10 IU in 500 ml10 IU in 1000 ml2 IU in 200 ml10 IU in 1000 ml
Without infusion set
0136610 drops
3026121220 drops
60412242430 drops
90824484840 drops
1201236727250 drops
1501648969660 drops
1802060120120
2102472144144
2402884168168
2703296192192

Table 5.

Low dose oxytocin infusion for induction and augmentation of labour. Version (1.0) 2021.

Oxytocin dose of greater than 20 mU/min highlighted in red can only be administer by a specialist or a senior resident doctor.

Prior to preforming AROM, an informed consent is necessary, and patient should be informed of the benefits of AROM and the possible complications therein and the fetal heart rate is checked. AROM can be performed with an Amniotomy finger cot (Amnicot) or Amniotomy hook (AmniHook) or a spinal needle for control release of amniotic fluid. The woman adopts a supine position and flexes her hips and knees (frog legged), or it can be done in the lithotomy position. A sterile glove finger is introduced using the dominant hand to performed vaginal examination and noting the cervical dilatation, effacement, position, station and to exclude cord presentation and possible vasa previa is noted. During the vaginal examination the amniotic perforator can be introduced with the non-dominant hand and the tip of the amniotomy hook is pushed against the sac with the index and middle finger guiding it and pull back. With successful rupture of membrane, the examining fingers should be held back to exclude cord prolapse and the amniotic fluid should be assessed for volume, colour, smell or particle within. It is good practice to recheck fetal heart and observe the woman closely for any vaginal bleeding [75, 76, 79]. For control release with spinal needle a bivalved speculum is required.

11. Complications of IOL and AOL

Artificial contractions are said to be more painful than spontaneous ones, more so the intensity and the duration might be more exaggerated than natural contractions. Therefore, the rates of complications associated with artificial uterine contractions are multiple folds compared with contractions from spontaneous onset [13]. The complications of IOL and AOL could range from tachysystole, hypertonus or an outright tachysystole with fetal heart rate abnormalities, placenta abruption or uterine rupture [80, 81] which occur in about 1–5% of women undergoing IOL. It is estimated that IOL could fail in 15% of patient with unfavourable cervix [81]. Both IOL and AOL could result in cord prolapse following AROM. There is a tendency of increasing the risk of infection, operative vaginal delivery and increased caesarean section rate [80] in women undergoing IOL. Poor childbirth experience was encountered in about 4.5% of patient undergoing IOL in a recent study to assess maternal childbirth experience [82]. The risk of primary post-partum haemorrhage in patients undergoing IOL is well documented [83]. Fetal complications can be in the form of fetal distress, meconium stained liquor and neonatal jaundice. Litigation from the abuse of oxytocin has been enormous in the past decade globally [84].

12. Conclusion

There is an increased rate of IOL especially across developed countries, however the unmet need for IOL in developing countries is bridged by the availability of misoprostol and Foley’s catheter at cost effective rates. Timely and appropriate IOL can lead to reduction in perinatal and maternal morbidity and mortality. Therefore, there is need for obstetricians and physicians that provide care in women’s health to keep abreast with the best external available evidence on the subject matter. It is important to employ the concept of respectful maternity in the pre-induction, induction, and post induction phase to improve outcomes, reduce litigations and enhance women satisfaction. A diagnosis of failed induction does not translate to automatic caesarean section if the fetal and maternal conditions are adjudged to be normal and stable; a pause and restart can be initiated after 24–48 h with lower threshold for intervention in the second cycle.

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Written By

Benjamin Joseph Nggada

Submitted: February 21st, 2022 Reviewed: March 10th, 2022 Published: April 29th, 2022