Early Human Development, 1977, l/l, 3-17 Biomedical Press 0 Elsevier/North-Holland

3

The induction and acceleration of labour: some benefits and complications

M.P.M.

RICHARDS

Unit for Research -on Medical Applications of Psychology, University of Cambridge, 5 Salisbury Villas, Station Road, Cambridge CBl 259, United Kingdom

Received

8 November

1976

Accepted

20 December

1976

INTRODUCTION

The merits of the increasing use of techniques for the induction and acceleration of labour continue to be widely debated in medical journals and elsewhere. A Lancet editorial [l] of 2 years ago stressed that further evidence was required before it could be asserted unequivocally that the benefits of these methods outweighed their disadvantages.* Though we still lack results from a large-scale randomized controlled trial, relevant evidence is steadily accumulating and it is my object to summarize the present position. My main focus is on the use of induction and acceleration techniques in the absence of clear-cut medical considerations. The ‘model’ situation I am considering is where a mother who has had an uncomplicated previous obstetric history and no problems during her present pregnancy who at her expected date of delivery or within 10 days of it is induced by amniotomy and this is immediately followed by an oxytocin infusion to augment her labour. Judging by national data and statistics published by some centres, between a third and a half of all inductions would fall into this definition. As this group of mothers and their babies can expect a very favourable outcome without an induction (perinatal mortality, for example, for such a group is probably about 8 per 1,000 in southern England), the use of active management techniques is only justified if the complications associated with their use are rare and have minimal consequences. *Despite this it is still easy to find confident statements of the value and benefit of these techniques. For example, Sir Norman Jeffcoate in his Simpson Memorial Lecture in 1976 [2] said that “induction rates of 20-50% are reported from most major Maternity Units in Britain, these being shown to give the best maternal and foetal results. . . . there is much evidence to show that, given reasonable selection it [induction] offers added safety and comfort”. He, like other writers in this vein, has yet to reveal where this reassuring evidence may be found.

4

As there is a great deal of variation in the way in which induction and acceleration techniques are used, wide generalizations are hard to substantiate but. in my discussion I will attempt to make it clear how far variations in techniques and their application influence the conclusions. The exact prevalence of active management techniques is not known. Eritish Health Service statistics show an increasing use of induction from 14% of hospital deliveries in 1963 to 37% in 1973 (provisional figures: 41% in 1974)*. Information in British Births Survey 1970 [3], suggests that in about half of these cases, artificial rupture of the membranes (ARM) will be immediately followed with oxytocin and this proportion has probably increased since 1970. In addition, some labours that begin spontaneously will be accelerated with oxytocin. Recently, prostaglandin E, has begun to be used in the place of oxytocin.

Perinatal mortality Rates of perinatal mortality have fallen as the use of active management techniques has increased. However, there is no decisive evidence that the two are at all closely related. Perinatal mortality rates are dominated by the incidence and outcome for low birth weight infants and those with congenital malformations. .About 70% of the first week deaths arise from the 6% of liveborn children weighing less than 2500 g and congenital malformations are associated with 22% of deaths [3]. Thus small variations in the outcome for full-term non-malformed infants will have little influence on the overall figures. Much of the improvement in perinatal figures can be accounted for by the smaller proportion of births to women of high parity and of an age outside the optimal range, the wider use of legal abortion and a probable improvement in general health of the mothers now having children. It remains to be demonstrated that changes in obstetric practice at delivery have had any influence in recent years. In an elegant paper, Yudkin [4] has demonstrated the difficulties in associating improvements in perinatal mortality with the increasing use of induction (or any obstetric or paediatric innovation) on the basis of the annual data available on births. Using information from the Oxford area [ 51 she shows that the improvement in perinatal mortality between 1965 and *These figures are derived from the British Health Service Hospital Inpatient Enquiry which is based on a 10% sample. The relevant codings cover both surgical rupture of the membranes (before labour starts) and oxytocin inductions. However, as there is no HIPE coding for spontaneous accelerated labour there may be confusions between induction and acceleration. The data will also suffer from the usual problems of information derived by retrospective coding of case notes. It is important to note that HIPE information only relates to hospital deliveries. Where a technique is largely confined to hospital deliveries, as is the case with induction the HIPE figures will not directly reflect changes in the whole population. Over the last decade hospital deliveries have risen from about 65 to 95%. So the rise in inductions recorded by HIPE for the hospital population will be less steep than that for all deliveries.

5

1972 could have occurred if induction had increased or decreased the chances of neonatal death. Neither a very high nor a very low incidence of induction is likely to be optimal for perinatal mortality. Selective use for medical indications can bring improvements but there is little agreement about size of the group with clear indications. O’Driscoll and his colleagues [6] suggest it is under 10% for primiparous women while others [7,8] assume it to be much larger. With very high rates of induction the complications may outweigh the gains so mortality rates may rise. On present evidence it is not possible to establish an upper limit. Much will depend on the selection of cases and the way in which techniques for the induction and acceleration are employed. It has been suggested [9] that unexplained deaths in mature infants may be reduced by high rates of induction. However, the perinatal survey figures show very little reduction in the proportion of post mature infants in spite of rising rates of induction [3,10]. In 1958 11.5% of babies were estimated to be of more than 42 wk gestation and 9.3% weighed more than 4000 g, the respective figures in 1970, with more than double the number of inductions were 11 and 8.2%. Of course there may be unknown factors which are tending to increase the incidence of post maturity. The available statistical evidence does not indicate that induction is employed very selectively at present. The age, parity and social class of induced women are very similar to those who are not induced [5], as are the distributions of the birth weights of their infants. As hospital policies toward induction differ widely, it is probable that the chances of a woman being induced will be more closely related to the characteristics of the institution where she delivers than to her personal characteristics. As the incidence of induction for non-medical reasons is unlikely to have more than marginal effects on perinatal mortality rates, it is more important to examine the influence on morbidity but, before I do this, I will discuss the possible benefits.

Advantages of induction and acceleration It is a great boon to mothers and their babies, as well as their attendants, that very long labours are now a thing of the past. However, as O’Driscoll has shown [6,11,12] this may be achieved with low induction rates. Under his system each mother is taught to expect delivery within 8 h of admission (patients being admitted in labour). His patient is placed in the care of one nurse who should remain with her, subject to normal hours of duty, until the baby is born. The use of techniques to control the duration of labour (though not routine induction and acceleration) have made the allocation of one nurse to one patient possible. The support provided for mothers means that only low levels of analgesics are required and the outcome seems excellent.

6

There are undoubtedly some women who would like to have their baby on a certain day. But, on the evidence of the widespread complaints about routine induction this group would appear to be smaller than the number who are currently induced for non-medical reasons. The group might be smaller still if mothers were informed of the possible complications of the technique for themselves and their babies [ 131. A substantial minority of women find surgical induction painful and for these patients it has been described as “a major psychological‘ordeal” by Caseby [ 141. In his series 22% of patients found the procedure painful without analgesia but this was reduced to 5% with the use of epidurals. It has been suggested that the greater predictability of deliveries and shorter labours that active management techniques can permit can lead to a reduction of the work load in maternity units. A series from Glasgow [ 151 indicates that very high induction rates do not necessarily mean a reduction , in night-time deliveries. In spite of the falling birth rate, the wider use of induction does not seem to have resulted in any reduction in staffing in maternity hospitals, though hours of work for some staff may have shortened. Savings may have been offset by the reduction in home deliveries. Though labours are shorter, more supervision is required if acceleration techniques are employed. The one-to-one patient-nurse system that could be possible is not all widely used so mothers are not necessarily receiving more support during actively managed labours [ 131. It has been argued that daytime delivery increases the chances of skilled assistance being close at hand, though conclusive evidence of the dangers of the night has not been forthcoming in Britain. Whether or not the dangers of the night are significant, the main impact of induction policies may have been to reduce births in the morning and create a peak later in the day. There is no national evidence that suggests night-time births have become rarer. While some centres have reported little change in the diurnal distribution of births with high rates of induction [ 151, others have experienced a reduction in the night-time work loads [16], emphasizing the wide variations in practice. One study has analysed the changing midwifery workload using a system of assigning 1 unit to a normal delivery, 2 units to forceps and other difficult deliveries, and 3 to caesarian sections. Inductions and admissions were given 0.5 units. Comparing 1976 with 1972 it was found that the total number of deliveries was reduced by 27% while the workload decreased by only ll%, indicating the increasing rate of intervention (inductions 28% to 51%, forceps from TABLE

I

Distribution

of work in a maternity

0900 to 1800 h 1800 to 2100 h 2100 to 0900 h

unit [ 16 ]

1972

1976

58% 13% 30%

71% 10% 19%

11% to 14% and caesarian sections from 11% to 15%). The changing distribution of the workload throughout the day and night (based on the unit system) is shown in Table I. Though in this hospital, night work has been reduced, it is important to note that 43% of night-time deliveries were classified as ‘abnormal’, so even with a high rate of induction there is a continuing need to provide skilled and experienced obstetric and paediatric cover around the clock. Another point that should be considered is costs. Direct evidence is not available but it seems likely that actively managed labours increase costs. As the major component in hospital costs is related to staff, much will depend on the number of deliveries per unit number of staff that a hospital achieves. Active management policies probably could be used to increase the ‘throughput’ of a hospital and so reduce costs but other considerations might make this undesirable. As we shall see below, widespread use of induction and acceleration may increase the need for expensive anaesthetic and paediatric facihties. In addition they may tend to increase the need for facilities for gestational assessment and monitoring during labour.

COMPLICATIONS

The possible complications that must be considered in any discussion of induction and acceleration are caesarian sections, forceps deliveries, maternal infection, increased use of analgesics and anaesthetics, respiratory depression and fetal distress, prematurity, neonatal jaundice and the separation of mother and baby. Each of these will be discussed in turn. Caesarian sections

Bonnar [ 171 (see also [ 181) has suggested that rates of non-elective caesarian section are increased by liberal induction policies while others [7] have argued the reverse.* Much may depend on the selection of cases, particularly with regard to the state of the cervix 117,191 and the use made of fetal monitoring techniques. In one series [8] where 27% of all patients were being induced for medical reasons, there was a section rate of 8%. The commonest indications for caesarian sections in induced patients were ‘failed induction’ (61% of caesarian sections in the induced group) and fetal distress (26%). The failed induction group included a preponderance of primigravid mothers with an unSfavourable cervix, poor descent of the head, who laboured a relatively lon, n time and required relatively high concentrations of oxytocin. *In some centres where induction rates have fallen recently, there have also been reductions in the percentage of caesarian sections. However, it is not clear whether this is because there is a close link between the induction rate and the caesarian section rate or because the reduced induction rate reflects a generally more conservative policy towards obstetric intervention.

8

What is certain is that section rates are rising, from 3.4% in 1964 to 4.9% in 1972 [20] .* However, the number of these done during labour is not known. Though this is now a safe operation (fatalities about 1 per 1000 sections [20]), it carries morbidity risks for mother and child. Sep, aration from the baby is much more likely after a section and there is more discomfort and forced immobility in the recovery period. Nursing the baby is more difficult for the mother and hospital stays are longer. The anaesthetic drugs (see below) and muscle relaxants [21] used for the operation may have undesirable effects on the baby. As a mother who has had a section is much more likely to require one for a subsequent delivery, the risks to her and to her children are cumulative.

Forceps

deliveries

Increasing rates of forceps deliveries may not be related to active management itself but to the use of epidural anaesthesia which is often associated with this style of obstetrics. The link between induction and epidurals is complex. Anaesthetics, including we may presume epidurals, are more commonly employed in induced births [5] and epidurals have been specifically recommended for the pain of an ARM [ 141. In some centres induc.. tion is used to ensure that a birth takes place when an anaesthetist is available to provide an epidural. However, there is no necessary connection between epidurals and induction except in so far as the added discomfort and pain of the latter (see below) will increase the chances of some analgesics or anaesthetic being used. Data from the Oxford area shows that the TABLE

II

Injuries

to the infant and the use of forceps

Injury

Spontaneous

cephalic

and vacuum Forceps

No.

%

No.

Cephalhaematoma Fractures Nerve injuries Other injuries None

115 5 7 1 13,704

0.8 0.0 0.0 0.0 99.1

68 2 3 0 1,346

Total

13,832

99.9

1,419

extraction and vacuum

cephalic

% 4.8 0.1 0.2 0.0 94.9 100.0

*These figures relate to all deliveries. HIPE statistics are often quoted to suggest that the percentage of sections is not increasing (as, for example, in the recent DHSS report on induction); however, these raw figures are misleading as they only concern hospital deliveries.

9

forceps rate when labour had been induced was about twice‘that occurring after spontaneous onset. Trauma is increased for both mother and child by a forceps delivery [ 121. The relationship with birth injuries is demonstrated by British Births Survey [3] (Table II). The bruising that can follow a forceps delivery may lead to neonatal jaundice (see below). The complications associated with the use of forceps often lead to separation of mother and baby and, therefore, possible difficulties in the establishment of their social relationship and lactation.

Ma ternal in fee tion Little investigation of this possible complication has been undertaken. However, the Cardiff Births Survey [22,23] suggests that increased rates of maternal urinary and genital infections are associated with induction and associated techniques. Infections are likely to be more common after forceps deliveries. Though infections are unlikely to have important clinical consequences, they will be an added burden for the mother during the lying-in period and will increase antibiotic use.

Analgesics and anaesthetics There is no doubt that many women find the contractions of an accelerated labour more painful so it is not surprising that narcotics and epidurals are being more widely used, especially as the provision of ‘personal’ nurses is not widespread and there appears to be little emphasis on emotional support [ 131 . According to the perinatal surveys pethidine was used in 56% of deliveries in 1958 and 68% in 1970 [ 3,101. This increase occurred despite the wider employment of epidurals which might be thought to act as a substitute. Data from the Oxford Record Linkage study area shows that anaesthetics are more commonly employed in induced births [ 51. Pethidine often causes nausea and vomiting in the mother and may produce unpleasant feelings of disorientation and unreality [ 12,131. It does not appear to be very effective as an analgesic [24]. Respiratory depression in the infant is well known with pethidine and is even more marked with Pethilorfan [25] . Though the depression may be reversed with narcotic antagonists like Lethidrone (nalorphine), hazards are associated with the use of these compounds. The British Births Survey [3] shows that they are given in the absence of a narcotic, which is likely to increase the depression in the baby, and infant deaths have occurred after the accidental confusion of Lanoxin with Lethidrone [ 261. Even in the absence of respiratory depression narcotics and other obstetric analgesics, anaesthetics (including epidurals) and tranquilizers can have profound effects on infant behaviour which may persist days, weeks

10

or even months after birth. The best-established of these include a reduction in muscle tone, an inhibition of nutritive sucking and an impairment of the ability to habituate to repeated sensory stimuli [ 27-331. These effects can lead to alterations in the mother--child relationship [ 321, make the establishment of lactation more difficult [30] and may reduce food intake for the baby [34]. There is little doubt of the efficiency of analgesia produced by epidurals and selective use of this technique can be of great value. However, in spite of the description of large series with few problems [ 351, its general use seems to be contra-indicated by the prevalence of complications [36] . In addition to the hazards for the baby already mentioned, epidurals can lead to maternal hypotension [37] and attendant complications for the fetus.and there is also the increased probability of a forceps delivery. Neurological complications for the mother, though rare, can be serious [38] . Epidurals may also extend labour and conceal a ruptured uterus [ 121. Maternal side-effects including nausea and faintness are common [14] and patient satisfaction is far from complete [39] .

Respiratory depression and fetal distress The onset of respiration

is delayed

after induced

births (Table III).

TABLE III Percentage of each group taking more than 3 min to establish regular respiration by method of induction [3] Method of induction

Number

Respiratory depression ratio

ARM alone with other methods

1,471 1,015

5.3 9.0

i.v. oxytocin alone with other methods

350 795

7.7 9.1

Buccal oxytocin alone with other methods

110 253

4.1 7.1

9,196

3.6

No induction

Of course, as the British Births Survey includes all births, in some cases delays in the onset of respiration may be explained by medical reasons that led to the induction. It is not known how many of these inductions were performed for clear medical indications. However, as mentioned earlier, many inductions are carried out at deliveries where an excellent outcome could be expected without this intervention. Without much better evidence it would be quite wrong to dismiss the raised incidence of respiratory depression as simply a result of increased proportion of complicated

11

cases in the induced group. Given a greater use of analgesics and anaesthetics, the stronger contractions that may occur during acceleration, and the possibility of uterine hypertonus, an increase in respiratory depression is not unexpected. The onus of proof would appear to rest with those who claim that induction does not increase respiratory depression to show this on the basis of a randomised controlled trial involving uncomplicated cases. The Glasgow trial [15] might appear to fit these criteria but unfortunately their ‘control’ group had a higher rate of induction than the national figure so that the study cannot provide a basis for the evaluation of typical practice. Other studies [40] have found an increased percentage of admissions to special care baby units after induction but the causes and effects of the induction are confounded. Data from the Cardiff Birth Survey [22,23,41] allow comparison of the effects of induction and acceleration rates of 19 and 6% on two large but comparable groups of women. Different rates of induction did not appear to be associated with differing admission rates to the special care unit. As the same paediatricians served the two obstetric teams, one may assume that the same criteria for admissions were applied to all the babies. The same survey suggests that fetal distress and moderately depressed infants (Apgar 4-7) have both become commoner since the late 1960s but incidence of both was similar for the two obstetric teams. Other studies have failed to find an increased incidence of fetal hypoxia after oxytocin in the absence of uterine hypertonus [ 421. Fetal distress has been associated with accelerated labours [ 43,441. Problems related to fetal distress are likely to vary with the technique used for administration of oxytocin, the dose used and fetal monitoring techniques. Some authors [ 71 have suggested that no patient should receive an oxytocin infusion without continuous fetal heart rate recordings. The British Births Survey 1970 indicates that only 61 patients had continuous fetal heart rate recordings during the sample week (3994 were induced). Though monitoring has become more widespread, it is unlikely that more than a small percentage of induced labours are monitored at present. It has been suggested that the fetal condition may be improved when the membranes remain intact until late in labour [46-481. Though intact forewaters may be less effective for dilating the cervix, the baby’s head may be protected from mechanical damage. Of course, most fetal monitoring techniques require ruptured membranes. Prematurity Induction, by definition, means that a baby is born earlier than it would be otherwise. In a few cases seriously pre-term births may be induced accidentally. In a series of 200 consecutive inductions, 13.4% babies were found to be more than 2 wk younger than assumed when assessed by Dubowitz scores and 5.5% had signs of immaturity but none had major problems [49]. However, in the 3 wk after this study ended, 2 induced babies had severe respi-

12

ratory distress syndrome. Both had been though to be near term but were found to be 4 and 8 wk less than the assumed age. Pre-term and immature babies are’ likely to need specialized paediatric care which will often entail separation from the mother. The incidence of unexpected immaturity will depend on induction policies and the methods used to estimate gestational age.* However, all of the latter carry some degree of uncertainty and there is not a perfect correlation between maturity and gestational age. Though the role of the fetal pituitary-adrenal axis in the initiation of labour is still unclear, glucocorticoids do appear to accelerate maturity of the lungs [50-521. Thus the functional maturity of the fetus and the initiation of labour may be closely tied together [ 531. If this were the case, at least a minor degree of immaturity would be expected with induction. This might explain the few term babies who develop respiratory distress syndrome after induction [ 441. The increasing use of induction has placed a much greater emphasis on the need to have an accurate assessment of gestational age. Ultra-sound scans and X-ray examinations are widely used for this purpose. On present evidence, the former is without significant risks (though it increases costs to the Health Service and the time mothers are required to spend in antenatal clinics) but the same cannot be said for X-ray examinations. The use of X-ray examinations in pregnancy is now as common as it was in the 1950s before the evidence linking it to cancers in children became available (and before ultrasound was available as a substitute), and in some regions more than 35% of women are exposed to X-rays during pregnancy [45].

Neonatal

jaundice

There is much disagreement about the possible link between the use of oxytocin and neonatal jaundice [55]. Statistical associations have been established in some studies, e.g. 56, 57, 58, but not in others, e.g. 59, 60. As similarly increased levels of bilirubin have been found after the use of prostaglandin E, in at least some studies [61] (though not all [62] ), it seems unlikely to be a pharmacological effect of oxytocin. What has been established is that in some centres the incidence of significant jaundice is rising. At Queen Charlotte’s for example a rise from 6.2% in 1969 to 15.5% in 1973 of infants with a peak of serum bilirubin of more than 206 mol/l was recorded [63]. In part, the rise seemed to be associated with increased use of epidural anaesthesia. Several possible factors may be associated with increased jaundice. One may be bruising during delivery even where it is not clinically noticeable. An association with forceps delivery has been suggested [64] , A link with *British figures for the proportion of births under 2500 g have been unchanging for several years while several European countries have shown an improvement. The available evidence does not allow us to confirm or refute the suggestion that our less favourable experience results from British induction policies.

13

bruising would account for the low rates of jaundice which have been noticed after caesarian section [ 611. Though long-term ill effects of raised bilirubin levels may be prevented by appropriate treatment, this will often involve separation of mother and infant. The use of techniques like phototherapy (and, occasionally, exchange transfusion) may upset parents, and in themselves perhaps carry risks. Jaundiced infants may be more difficult to feed and this, together with the effects of analgesics, may be the explanation of reports [13] of feeding problems after induction.

Separation

of mother and in fan t

Given that many of the complications that may be associated with induction ,and acceleration require paediatric intervention, it is not surprising that rates of admission to special care baby units are increasing with the wider use of active management techniques. DHSS statistics show a rise from 12% of all infants in 1970 to 17% in 1974. Though changing admission policies may account for some of the increase [3,65] alterations in the use of various obstetric techniques may also be involved. It is now reasonably well established that early separation and admission to a special care unit can have deleterious effects on the mother’s relationship with her babies for months [66-701, if not years [71,72]. Even where mothers are encouraged to visit their babies in such units, their confidence in being able to cope with child care after discharge seems to be reduced [ 731. It has also been suggested that early separation could be a precipitating factor in non-accidental injury of children [ 741. Neonatal special care facilities are very expensive to provide. If the need for them could be reduced, resources might be released for other very desirable purposes. An association between sudden unexpected death in infants aged less than 12 wk and induction has been reported [ 751. Though pre-term babies are more likely to die in this way [76] , the gestational age of the infants cannot explain this association with induction. The nature of the link is unknown. ‘However, there are indications that central nervous system damage may be unusually common in at least some samples of infants who died suddenly and unexpectedly and that this may result from moderate neonatal jaundice and/or lack of oxygen [ 771.

CONCLUSIONS

On the present evidence it is not possible to assess the extent of morbidity that may be associated with the wider use of induction and acceleration of labour. Much will depend on the policies governing the use of these methods and the techniques employed. Randomized controlled trials would be very desirable and should provide much more precise answers to many of the

14

questions. Trials should be multi-centre to assess the effects of varying policies and techniques and differences that might arise from population variation. As well as assessing the strictly medical factors, it is to be hoped that trials would investigate convenience to patients and staff and estimate costs. In the absence of more definitive evidence, the studies that I have reviewed do indicate that some caution may be required. In the absence of clear medical or social benefits, the complications of these techniques may well outweigh any factors of convenience, particularly if the possibilities of a disturbed mother-baby relationship are taken into account.

ACKNOWLEDGEMENTS

I am grateful to Dr. Iain Chalmers for permission to use unpublished data from the Cardiff Birth Survey; also to him, Professor T. Chard, Professor A. Turnbull, Dr. P. Dunn and Dr. N.R.C. Roberton for comments on an earlier draft of this paper. REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

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39

40 41 42 43 44 45 46

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The induction and acceleration of labour: some benefits and complications.

Early Human Development, 1977, l/l, 3-17 Biomedical Press 0 Elsevier/North-Holland 3 The induction and acceleration of labour: some benefits and com...
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