Is routine induction oflabour at term ever justified?

Linda Cardozo

Balancing the risks of prolonged gestation againstthose ofinduced labour is difficult. Risks to the fetusincrease slightly after 42 weeks' gestation but womenhaving labour induced are more likely to haveinstrumental deliveries or babies with low Apgarscores. Since many women are now expressing apreference for minimal interference in childbirth themost acceptable management of post-term preg-nancy seems to be increased fetal surveillance. Eachcase needs to be considered individually and it isimportant that the woman is involved in the decisionto induce.

Although the World Health Organisation defines termas 37-42 completed weeks of pregnancy (259-294days), most pregnant woman and many midwivesthink of term as the expected date of delivery. Womenare given an expected delivery date that is calculated as40 weeks (280 days) after the first day of the lastmenstrual bleed. But it is uncommon for the baby toarrive on that date, and women find it disappointingand sometimes worrying if delivery does not occursoon after this time. Perhaps we should reconsiderwhether it is necessary to give women a precise date onwhich they should expect their baby to arrive.

Accurate dating of pregnancy is important for otherreasons, such as prenatal diagnosis and early identifica-tion of intrauterine growth retardation. In addition,ultrasonographic dating has been shown to reduce theincidence of truly prolonged pregnancy from about10% to as low as 1%.' Even amongwomen who are sureof their dates the incidence of post-term pregnancy canbe halved if an early ultrasound scan is performed.This is important as the outcome for women whoselabour is induced for "uncertain postmaturity" issignificantly worse than for those who have labourinduced at 42 weeks' gestation.2

King's College Hospital,London SE5 9RSLinda Cardozo, consultantobstetrician and gynaecologist

BMJ 1993;306:840-1

Risks ofpost-term pregnancyPerinatal mortality is lowest at 40 weeks' gestation

and does not increase until after 42 weeks, and thenonly slightly. But because some intrauterine deathswill always occur before 42 weeks it might seemsensible to deliver all babies at 42, 41, or even 40weeks. The problem is induction of labour. Inducedlabour is longer and is associated with more instru-mental deliveries, an increased risk of postpartumhaemorrhage, and perhaps most importantly, a higherincidence oflow Apgar scores than spontaneous labour.If the point of inducing labour is to reduce risks to theneonate then it may be failing.'

Before intravaginal prostaglandins were used regu-larly to ripen the cervix women having labour inducedwere more likely to need caesarean section, whichcarries a risk of morbidity (and increased risk ofmortality) for the mother. However, the Canadianmulticentre post-term pregnancy trial group foundthat women allowed to go into labour spontaneouslyhad a higher rate of caesarean section (24'5%) thanthose who had labour induced (21202%) because of anincreased incidence of fetal distress in the first stage.4Unfortunately, the group did not define fetal distress,and the increased incidence may have been related to

the higher rate of meconium staining of the amnioticfluid in spontaneous labours, which is to be expectedat a later gestation. There was no difference in theincidence of meconium aspiration, one of the greatestneonatal risks of prolonged pregnancy; nor were anyother differences in perinatal outcome recorded. Theintervention rate (instrument and operative delivery)in this large study of 3407 uncomplicated prolongedpregnancies, was 49% among women randomised toinduction of labour and 51% for those who weremonitored while awaiting spontaneous labour. In theUnited Kingdom many midwives, obstetricians, andmothers would consider this an unacceptably highlevel of intervention in an otherwise normal physio-logical process.Women who go into spontaneous labour before their

estimated date of delivery are fortunate as the risks toboth mother and baby have been shown to increase as"term progresses."' But there is no evidence thatinducing labour improves the outcome for mother orbaby.6 Many women see induction as interference witha natural process and it is one of the reasons why theywrite "birth plans."

When to induceIf routine induction of labour at term cannot be

justified, when should intervention occur? Bergsjo et alsuggested 43 weeks' gestation7 as induction at this timehas a lower incidence of failure.8 However, a fixed cutoff point seems unnecessarily prescriptive. Each caseneeds to be considered individually and timing of

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delivery should be based on the woman's risk factors.Earlier induction of labour would obviously be prefer-able for a 40 year old primigravid woman with a longhistory of infertility, even after an uncomplicatedpregnancy, whereas it may be inappropriate for a 25year old multiparous woman.The state of the cervix (Bishop's score) should also

be considered. If delivery with an unfavourable cervixis thought essential it may be better to deliver byelective lower segment caesarean section under epiduralblock than to risk the need for an emergency caesareansection under general anaesthesia in the middle of thenight. Emergency caesareans carry a much higher riskof morbidity and mortality to the mother and asphyxiato the baby. Recent data from King's College Hospitalhave shown an unacceptable incidence ofunrecognisedmatemal morbidity associated with caesarean sectionand this may be compounded by the need for repeatedoperative delivery in subsequent pregnancies.9

Alternatives to inductionIs there anything we can do for women who go past

term? Membrane stripping has been suggested toproduce earlier spontaneous labour and have nocomplications,'0 but it is also an intervention that manywomen would dislike. The best policy is probably tooffer increased fetal surveillance after 42 weeks (orearlier if risk factors are present) and to terminatethe pregnancy if adverse features occur. Pearce andMcParland showed that the most sensitive measure inantenatal fetal surveillance is absence of end diastolicfrequencies in the umbilical artery (assessed byDoppler ultrasonography).II This predicted 91% offetuses who became distressed in the first stage oflabour, and combination with ultrasonographic esti-mation of the volume of amniotic fluid improved

prediction to 100% with only a slight fall in specificity.Perhaps the most important part of managing post-

term pregnancy is involving the woman and herpartner. The decision to induce or not should bediscussed, and if possible the woman's views respected.I discuss induction of labour at 42 weeks' gestation inan otherwise uncomplicated pregnancy and offer it ifthe cervix is favourable and the woman keen to bedelivered. I encourage women to have induction at 43weeks' gestation because of the slightly increased riskto the baby thereafter. Unfortunately, there is no"right time" to induce nor any conclusive data onwhich to base a rational decision.

1 Boyd ME, Usher RH, McClem FH, Kramer MS. Obstetric consequences ofpostmaturity. AmJ Obstet Gynecol 1988;158:334-8.

2 Gibb DMF, Cardozo LD, Studd JWW, Cooper DJ. Prolonged pregnancy: isinduction of labour indicated? A prospective study. Br J7 Obster Gynaecol1982;89:292-5.

3 Cardozo LD, Fysh J, Pearce JM. Prolonged pregnancy-the managementdebate. BMJ 1986;293:1059-63.

4 Hannah ME, Hannah WJ, Hellmann J, Hewson S, Milner R, Willan A and theCanadian multicenter post-term pregnancy trial group. Induction of labor ascompared with serial antenatal monitoring in post-term pregnancy. Arandomised controlled trial. NEnglJMed 1992;326:1587-92.

5 Saunders N, Paterson C. Effect of gestational age on obstetric performance:when is "term" over? Lancet 1991;338:1190-2.

6 Chapatte 0, Versi E. Gestational age and obstetric performance. Lancet1992;339: 122.

7 Bergsio P, Gui-dan H, Su-qui Y, Zhi-zeng G, Bakketeig LS. Comparison ofinduced versus non-induced labor in post-term pregnancy. Acta ObstetGynecolScand 1989;68:683-7.

8 Augensen K, Bergsjo P, Eikeland T, Askrik K, Carlsen J. Randomisedcomparison of early versus late induction of labour in post-term pregnancy.BMJ 1987;294:1 192-5.

9 Kelleher C, Cardozo LD. Caesarean section-unrecognised morbidity.J Obstet Gynaecol (in press).

10 McColgin SW, Hampton HL, McCaul JF, Howard PR, Andrew ME,Morrison JC. Stripping membranes at term: can it safely reduce theincidence ofpost-term pregnancies? Obstet Gynecol 1990;76:678-80.

11 Pearce JM, McParland PJ. A comparison of Doppler flow velocity waveforms,amniotic fluid columns and non-stress test as a means ofmonitoring postdatepregnancies. Obstet Gynecol 1991;77:204-8.

(Accepted 28January 1993)

Lesson ofthe Week

Acute haemolysis induced by high dose ascorbic acid inglucose-6-phosphate dehydrogenase deficiency

D C Rees, H Kelsey, J D M Richards

The use ofhigh dose ascorbic acid (vitamin C) has beenadvocated for a wide range of ailments for years. Suchtreatments are generally thought to have few adverseeffects and are often self administered. We present acase illustrating the particular caution necessary insubjects at risk of glucose-6-phosphate dehydrogenasedeficiency.

Case reportA 32 year old man bom in Britain of Nigerian

parents was admitted as an emergency case complain-ing of breathlessness, dark urine, and left subcostalpain radiating to the left shoulder. His history includedmalaria caught in Nigeria at the age of 11 and treateduneventfully with quinine. There was no familyhistory of haemolytic crises and he had been healthyuntil December 1991, when he was found to haveantibodies to HIV- 1. There were no known risk factorsfor HIV infection. The exact source of the infectionwas unclear. His CD4 lymphocyte count was0 35x 1O9/l. He had remained well until June 1992,when he developed generalised lymphadenopathy andhis doctors recommended that he should start zido-

vudine. He had refused, however, and sought adviceprivately from a medically qualified nutritionist. Anextensive nutritional screen was performed, includingmeasurements of blood mineral, vitamin, and fattyacid concentrations. Among several abnormalitiesnoted were low serum and red cell glutathione concen-trations (red cell glutathione 1 1 mmol/l (normal1 6-2-8 mmoIl/), serum glutathione 3-2 ,umol/l(normal 3-8-8&2 ,umol/l)).He was prescribed a course of multivitamins, essen-

tial fatty acids, and glutathione supplements. He wasalso prescribed a course of high dose intravenousascorbic acid, 40 g three times weekly, supplementedby 20-40 g ascorbic acid daily by mouth. This pro-ceeded uneventfully for about a month with no obviousevidence of either haemolysis or regression of lympha-denopathy. The intravenous dose was increased to80 g, and next day the patient became breathless andfeverish and noticed that his urine was black. Hissymptoms worsened over the next two days and heretumed to the nutritionist.

Results of blood tqsts were: haemoglobin concentra-tion 67 g/l, white cell count 127 x 1 0/1, platelet count198x 109/1, reticulocyte count 15-6%, bilirubin concen-

High dose ascorbicacid can causehaemolysis in glucose-6-phosphatedehydrogenasedeficiency

Department ofHaematology, UniversityCollege Hospital, LondonWC1E 6AUD C Rees, registrar inhaematologyH Kelsey, researchfellow inhaematologyJ D M Richards, consultant inhaematology

Correspondence to:Dr Richards.

BMJ 19933:841-2

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