To determine if prolonged active phase of labour is associated with increased risk of uterine scar rupture in labour following previous lower segment caesarean section, a retrospective cohort study (1988-91) was done to analyse active phase partographs of 236 patients undergoing trial of labour following caesarean section, 7 (3%) of whom had scar rupture. After onset of active phase (3 cm cervical dilatation), a 1 cm/h line was used to indicate  alert . A zonal partogram was developed by dividing the active phase partographs into 5 time zones: A (area to the left of  alert  line), B (0-1 h after  alert  line), C (1-2 h after  alert  line), D (2-3 h after  alert  line) and EF (\u3e 3 h after  alert  line). The relative risk of uterine scar rupture was calculated for different partographic time zones. The relative risk of uterine scar rupture was 10.5 (95% confidence interval 1.3-85.5, p = 0.01) at 1 hour after crossing the  alert  line; 8.0 (95% confidence interval 1.6-40.3, p = 0.009) at 2 hours after crossing the  alert  line; and 7.0 (95% confidence interval 1.6-29, p = 0.02) at 3 hours after crossing the  alert  line. In women undergoing trial of labour following caesarean section, prolonged active phase of labour is associated with increased risk of uterine rupture. A zonal partogram may be helpful in assessing this risk in actively labouring women who cross the partographic  alert  line

Khan, K S

Rizvi, A

Rizvi, J H

English

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eCommons@AKUDepartment of Obstetrics & Gynaecology Division of Woman and Child HealthJune 1996Risk of uterine rupture after the partographic 'alert'line is crossed--an additional dimension in thequest towards safe motherhood in labour followingcaesarean sectionK S. KhanAga Khan UniversityA RizviAga Khan UniversityJ H. RizviAga Khan University, javed.rizvi@aku.eduFollow this and additional works at: https://ecommons.aku.edu/pakistan_fhs_mc_women_childhealth_obstet_gynaecolPart of the Obstetrics and Gynecology CommonsRecommended CitationKhan, K. S., Rizvi, A., Rizvi, J. H. (1996). Risk of uterine rupture after the partographic 'alert' line is crossed--an additional dimensionin the quest towards safe motherhood in labour following caesarean section. Journal of Pakistan Medical Association, 46(6), 120-122.Available at: https://ecommons.aku.edu/pakistan_fhs_mc_women_childhealth_obstet_gynaecol/151Risk of Uterine Rupture after the Partographic ‘Alert’ Line isCrossed - An Additional Dimension in the Quest Towards SafeMotherhood in Labour Following Caesarean SectionPages with reference to book, From 120 To 122 Khalid S. Khan, Asad Rizvi, Javaid H. Rizvi ( Department of Obstetrics and Gynaecology, Aga Khan University MedicalCentre, Karachi. ) Abstract To determine if prolonged active phase of labour is associated with increased risk of uterine scarrupture in labour following previous lower segment caesarean section,a retrospective cohort study(1988-91) was done to analyse active phase partographs of 236 patients undergoing trial of labourfollowing caesarean section, 7 (3%) of whom had scar rupture. After onset of active phase (3 cmcervical dilatation), a 1 cm/h line was used to indicate “alert”. A zonal partogram was developed bydividing the active phase partographs into 5 time zones: A (area to the left of “alert” line), B (0-1 h after“alert” line), C(1-2 h after “alert” line), D (2-3 h after “alert” line) and EF (>3 h after “alert” line), Therelative risk of uterine scar rupture was calculated for different partographic time zones. The relativerisk of uterine scar rupture was 10.5 (95% confidence interval 1.3-85.5, p=O.Ol) at 1 hour aftercrossing the “alert” line; 8.0(95% confidence interval 1.6-40.3, p=0.009) at 2 hours after crossing the“alert” line; and 7.0(95% confidence interval 1.6-29, p=O.O2) at 3 hours after crossing the “alert” line.In women undergoing trial of labour following caesarean section, prolonged active phase of labour isassociated with increased risk of uterine rupture. A zonal partogram may be helpful in assessing thisrisk in actively labouring women who cross the partographic “alert” line (JPMA 46:120, 1996).Introduction In the prevention of uterine rupture in women undergoing a trial of labour following caesarean section,timely diagnosis and prompt management of labour dystocias has been recommended1.. Chazotte andCohen2 have commented that “arrest disorders might indicate or predispose a patient to uterine rupture,a trial of labourshouldbe discontinued if there is no prompt response to uterine stimulation”. However,there is controversy about the upper limit of duration of normal active phase of labour3 and the lengthof labour beyond which the increased risk of uterine rupture in women with previous caesarean sectionwarrants intervention is not clearly known.This retrospective cohort study evaluates the relationship between prolonged labour during the activephase and uterine scar rupture in women having a trial of labour following a previous caesareansection. “prolonged labour” is defined as crossing of a partographic “alert” line during active phase and“uterine rupture” is defined as a uterine scar separation necessitating operative intervention lateralpelvimetry. Women with more than one caesarean, a classical caesarean, placentapreviaorrefusal toundergo a trial had a repeat elective caesarean (n=152) and were excluded. Partographic records couldnot be retrieved in 10 cases, 9 of vaginal deliveiy and 1 of caesarean section due to “fetal distress”.Thus, in total 236 ase.s were evaluated.Subjects and Methods The AgaKhan University Department of Obstetrics and Gynaecology provides secondaiy and tertiarylevel care to a largely self- referred population. During 1988-91, out of 398 consecutive patients withprevious caesarean section, 246 (67.8%) were selected for a labour trial based on the presence ofa non-recurrent cause forcaesareansection and an adequate maternal pelvis, as judged by clinical assessmentand erectAll patients signed an informed-consent and were managed according to a uniform policy duringlabour. Partograms were commenced according to the WHO guide lines4 . Vaginal examination wereperformed every 2-4 hours or earlier if indicated. After the diagnosis of active phase (labour establishedwith regular uterine contractions and cervical dilatation of 3 cm) a 1 cm/hour line was used as the“alert” line. Fetal heart rate was continuously monitored throughout labour. Amniotomy and oxytocinwere used for the same indications as for patients with unscarred uteri. The initial dose of oxytocin, 1mIU/min, was doubled eveiy 30 min until the patient had adequate uterine activity (3-4 contractions in10 min, each lasting for 45 seconds) or until the maximum dose of32 mIU/min was reached.Partograms were analysed by drawing at each hour after the “alerf line 3 lines which divided thepartogram into zones A,B,C,D,E and F as shown in Figure.In the definition of prolonged active phase there is controversy about the lag time after the “alert” line3.We, therefore, used three different lag times.afterthe “alert” line in analysis: firstwith 1 hourlagtimemaking zones A-B normal and C-F prolonged; second with 2 hour lag time making zones A-C normaland D-F prolonged; and third with 3 hour lag time making zones A-D normal and E-F prolonged. Ournull hypothesis was one of no association between active phase labour prolongation and uterine scarrupture.We tested the null hypothesis for each one of the three lag times by calculating and comparing rupturerates for normal and prolonged labour. The differences in baseline characteristics were tested withanalysis ofvariance andtestof linear trend. Relative risk (95% confidence inteivals) and Fisher’s exacttest were used for analysing the differences in rate of scar rupture according to different definitions ofprolonged active phase. Statistical analysis was performed with Epi Info software (version 6.0, Centresfor Disease ContrOl, Atlanta, U.S.A.).Results Successful vaginal delivery was achieved in 190 (77.2%) out of the total of 246 cases. Of the rest (56),26 cases had repeat caesarean section for slow progress of labour in the first stage, 2 had caesareansections for non-descent of foetal head in the second stage, 27 had caesarean sections for “fetaldistress” (abnormal cardiotocographic trace with or without meconium and fetal scalp pH of <7.2) and1 had caesarean section for suspected scar rupture during the second stage of labour. There were-7 (3%)cases of uterine scar rupture.The general characteristics of the 236 subjects whose partograms were analysed are shown in Table I.There was no difference in the distribution of the age, parity, gestational age at delivery and birthweight in the different partographic zones withthe exceptionof use ofoxytocin. Outofthe 7 cases of scarrupture, 1 patient was in zone B (1-2 hour period beyond the “alert” line), 3 patients were in zoneD (2-3 hourperiodbeyond the “alert” line) and 1 patient each was in zones E & F (beyond the3 hourline).Table II shows the relative risks (95% confidence intervals) of having a uterine scar rupture if thelabour was prolonged according to different lag times afterthe “alert” line.The risk increased by 10.5 times (95% confidence interval 1.3-85.5) for the 1 hour lag time after “alert”line; by 8 times (95%confidence interval 1.6-40.3) for the 2 hour lag time after “alert” line; and by 7times (95% confidence interval 1.6-29) for the 3 hour lag time after “alert” line.Discussion The aetiology of uterine scar rupture during trial of labour following caesarean section is believed toarise from excessive tension generated during the active phase, which has a cumulative effect as labourbecomes prolonged. However, until recently this association was not subjected to epidemiologicalscrutiny. Leung et al5 were probably the first to show in a case-control study, an association betweenprolonged labour and uterine rupture in cases of trial of labour following previous caesarean section(women with uterine scar rupture were more likely to have been exposed to labour dysfunction than thecontrol group with odds ratio: 7.2,95% confidence interval: 2.6-19.8). In their paper, prolonged labourwas defined as active phase protraction (cervical dilatation rate <1.5 cm/h) or arrest of dilatation for >2h. However, the measurement of duration of labour or the rate of its progress is subjective, particularlythe demarcation between the end of latent phase and the onset of active phase can have largeinter/intraobserver variation. The criteria for defining onset of active phase were not cleariy delineatedby Leung et al6 raising doubts about the accuracy of assessing exposure to prolonged labour.In our cohort study, the relative risk of uterine rupture in cases of prolonged labour was similar in sizeto the odds ratio reported by Leung et al5 but the confidence intervals in our analysis were larger. Thisassociation between prolonged labour and uterine scar rupture cannot be explained on the basis ofchance alone as the p value was <0.05 and the lower confidence limit was above one, but there arepossible confounders and biases. In our analysis, the confounders were equally distributed mall thepartographic zones except the use of oxytocin which showed a linear trend with prolonging labour(Table I). This is not unusual as the use of oxytocin to augment slow labour is considered safe inpatients with previous caesarean section. We also attempted to minimise the biases arising from thedifficulty in accurate assessment of exposure to prolonged active phase by the use of a more objectivetool for assessing progress of labour, the partognun.The precision of our findings is limited by the small sample size but it provides a useful frame-work toanalyse the active phase partograms in trial oflabourfollowing caesarean section. The next step shouldbe to cariy out further prospective cohort studies with objective and unbiased assessment of labourprogress in order to determine the length of labour beyond which the risk of uterine rupture (and itscomplications) becomes far too high to exceed the expected benefits of vaginal delivery. We would,therefore, like to invite other researchers in Pakistan to perform similar analyses of partograms inwomen undergoing trial of labour following caesarean section in their obstetric units. Such acollaborative effort would be the first step in the right direction in developing nation-wide guidelinesfor the safe conduct of labour in women with previous caesarean section.The aetiology of uterine scar rupture during trial of labour following caesarean section is believed toarise from excessive tension generated during the active phase, which has a cumulative effect as labourbecomes prolonged. However, until recently this association was not subjected to epidemiologicalscrutiny. Leung et al5 were probably the first to show in a case-control study, an association betweenprolonged labour and uterine rupture in cases of trial of labour following previous caesarean section(women with uterine scar rupture were more likely to have been exposed to labour dysfunction than thecontrol group with odds ratio: 7.2,95% confidence interval: 2.6-19.8). In their paper, prolonged labourwas defined as active phase protraction (cervical dilatation rate <1.5 cm/h) or arrest of dilatation for >2h. However, the measurement of duration of labour or the rate of its progress is subjective, particularlythe demarcation between the end of latent phase and the onset of active phase can have largeinter/intraobserver variation. The criteria for defining onset of active phase were not cleariy delineatedby Leung et al6 raising doubts about the accuracy of assessing exposure to prolonged labour.In our cohort study, the relative risk of uterine rupture in cases of prolonged labour was similar in sizeto the odds ratio reported by Leung et al5 but the confidence intervals in our analysis were larger. Thisassociation between prolonged labour and uterine scar rupture cannot be explained on the basis ofchance alone as the p value was <0.05 and the lower confidence limit was above one, but there arepossible confounders and biases. In our analysis, the confounders were equally distributed mall thepartographic zones except the use of oxytocin which showed a linear trend with prolonging labour(Table I). This is not unusual as the use of oxytocin to augment slow labour is considered safe inpatients with previous caesarean section. We also attempted to minimise the biases arising from thedifficulty in accurate assessment of exposure to prolonged active phase by the use of a more objectivetool for assessing progress of labour, the partognun.The precision of our findings is limited by the small sample size but it provides a useful frame-work toanalyse the active phase partograms in trial oflabourfollowing caesarean section. The next step shouldbe to cariy out further prospective cohort studies with objective and unbiased assessment of labourprogress in order to determine the length of labour beyond which the risk of uterine rupture (and itscomplications) becomes far too high to exceed the expected benefits of vaginal delivery. We would,therefore, like to invite other researchers in Pakistan to perform similar analyses of partograms inwomen undergoing trial of labour following caesarean section in their obstetric units. Such acollaborative effort would be the first step in the right direction in developing nation-wide guidelinesfor the safe conduct of labour in women with previous caesarean section.Acknowledgements The authors am grateful to Professor S.C. Robinson for his encouragement and support of this projectand to all the consultants and staff for their untiring efforts in the management of patients with trial oflabour following caesarean section during the course of this study.References 1. Farmei R.M., Kirschbaum. 1., Potter. D. d al. Uterine rupture during that of labour after previouscaesar ean section. Am. J. Obstet. Gynecol., 1991;165:996. 1001.2. Chazotte, C. and Cohen, W.R. Catastrophic complications ofprevious caesarean section. Am. J.Obstd. Oynecol., 1990;163:738-742.3. Crowthe, C.,Enkin,M..Keirse,M.N.J.C.Monitoring the progress of labour. In: Effective Care inPregnancy and Childbirth Vol. 2 (Chalmers, I.. Kierse, M.N.J.C. and Enkin. M,). Oxford, Oxford Univ.Press, 1989, pp. 833.845.4. World Health Organisation. The partograph: A managerial tool for the prevention of prolongedlabour. Section II: A Users Manual. Geneva, WHO, 1988.5. Leung. AS., Farmer, R.M., Leung, E.K. et al. Risk factors associated with uterine rupture during trialof labour alter caesarean delivezy. A case.control study. Am.J. Obstet. Gynecol., 1993;168:1358-1363.

Risk of uterine rupture after the partographic \u27alert\u27 line is crossed--an additional dimension in the quest towards safe motherhood in labour following caesarean section

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Risk of uterine rupture after the partographic \u27alert\u27 line is crossed--an additional dimension in the quest towards safe motherhood in labour following caesarean section

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