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Objective To determine the relationship between decision to delivery interval and perinatal outcome in severe placental abruption.
Design A case–control study.
Setting Large inner city teaching hospital.
Methods Retrospective case note review of pregnancies terminated following severe placental aburption and fetal bradycardia. One year paediatric follow up by case note review or postal questionnaire. The differences in outcome (death or cerebral palsy) were examined using non-parametric and univariate analysis for the following time periods — times from onset of symptoms to delivery, onset of symptoms to admission, admission to delivery, onset bradycardia to delivery and decision to delivery interval.
Main outcome measures Prenatal death or survival with cerebral palsy.
Results Thirty-three women with singleton pregnancies over 28 weeks of gestation, admitted with clinically overt placental abruption, where delivery was effected for fetal bradycardia. Eleven of the pregnancies had a poor outcome (cases), eight infants died and three surviving infants have cerebral palsy. Twenty-two pregnancies had a good outcome (controls): survival with no developmental delay. No statistically significant relationship was found between maternal age, parity, gestation, or birthweight and a poor outcome. A statistically significant relationship between time from decision to delivery was identified (P= 0.02, Mann–Whitney U test). The results of a univariate logistic regression for this variable suggest that the odds ratio of a poor outcome for delivery at 20 minutes compared with 30 minutes is 0.44 (95% CI 0.22–0.86). Fifty-five percent of infants were delivered within 20 minutes of the decision to deliver. Serious maternal morbidity was rare.
Conclusion In this small study of severe placental abruption complicated by fetal bradycardia, a decision to delivery interval of 20 minutes or less was associated with substantially reduced neonatal morbidity and mortality.
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Placental abruption is a significant cause of maternal and neonatal morbidity and mortality. Maternal complications include haemorrhagic shock, coagulopathy and disseminated intravascular coagulation, uterine rupture, renal failure and ischaemic necrosis of distal organs1,2. Neonatal complications include death and neurodevelopmental problems1,3.
Much of the perinatal mortality and maternal complications occur when women are admitted with a severe abruption with an intrauterine death. This represents the most severe form of the disease. It is less clear what the risks are for less severe forms of abruption although there is evidence suggesting degrees of long term neonatal disability3–8.
Clinicians confronted with severe abruption and a live fetus have the dilemma of balancing risks for the mother of possible abdominal surgery in a haemodynamically unstable individual with a possible coagulopathy versus possible risks of increased mortality and serious morbidity to the fetus of delay. There is evidence that if the fetal heart rate pattern is normal, then delay such that the maternal status is stabilised, is appropriate1,2,9–13. However, the effects of actions of staff are less clear when the fetal heart rate pattern is already severely abnormal. With the adoption of standards for decision to delivery intervals for abnormal labour14, the organisation and ability of maternity services to react rapidly has come under scrutiny. We wished to examine if these time intervals or other factors influenced outcome in severe abruption.
We have examined a group of pregnancies complicated by severe revealed placental abruption with fetal bradycardia.
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Computerised maternity records and Delivery Suite registers from 1990 to 1999 were searched for all documented occurrences of severe antepartum haemorrhage. Records and summaries of perinatal mortality meetings were scrutinised to identify additional study patients. During this period there were approximately 70,000 births. Nine hundred occurrences of severe antepartum haemorrhage were identified. Preliminary screening excluded those where delivery was not performed for fetal distress. The remaining records were reviewed by one of us (S.K.). Occurrences fulfilling the following criteria were selected:
Gestational age more than 28 weeks,
Placenta praevia excluded at delivery,
Fetus alive on admission,
Emergency caesarean section for fetal distress.
All occurrences where an electronic recording of the fetal heart rate was available were reviewed initially by one of us (S.K.). Occurrences where a fetal bradycardia was described and all occurrences without electronic monitoring were reviewed by two authors (S.K., S.W.). Occurrences where a persistent profound fetal bradycardia, defined as a fetal heart rate less than 90 beats per minute for more than 3 minutes, and where the decision to deliver was instituted as a consequence were selected. Occurrences where the fetal heart rate subsequently recovered were excluded. In the presence of auscultated fetal heart rate recordings, occurrences were excluded if any recording was above 90 beats per minute prior to the last recorded rate.
The outcome of the pregnancy was classified as poor (cases) or good (controls) with a poor outcome defined as neonatal death or cerebral palsy. Data to determine case–control status were obtained in three ways. If formal follow up was carried out, then data were abstracted from the paediatric case records. Where no or limited follow up was available, the primary care team was identified and contacted. They were asked if the child was normal, or had developmental delay, cerebral palsy or other handicap. Primary care practitioners were asked to give as much detail as they wished. All infants were at least one year old at the time of the initial inquiry. As a final check, if a subsequent pregnancy had occurred, the records were examined for details of long term outcome for the previous infant.
From the records of the cases and controls the following information was extracted: demographic details, gestation (as determined by ultrasound prior to 20 weeks of gestation), history of smoking or substance abuse, past obstetric history and any current antenatal problems. Details of the time of onset of symptoms, time of admission to hospital, type of presenting symptom, fetal heart rate on admission (sonicaid, cardiotocograph or ultrasound), time of onset of bradycardia, time of decision to deliver and time of delivery were identified and extracted. The time of the first recorded heart rate of less than 90 beats per minute was noted, and is designated as the time of onset of bradycardia. A fetal heart rate of less than 90 beats per minute at the time of admission was entered as the time of onset of bradycardia. This includes fetal heart rate only detected by ultrasound in some cases. Data were collected on any investigations performed at admission and during hospital stay. Wherever continuous electronic fetal heart rate monitoring was available, it was divided into 5 minute epochs and the duration of bradycardia was noted. When no electronic monitoring was available, the duration of bradycardia was either the admission to delivery interval (where the heart rate was less than 90 beats per minute on admission) or the time from first recorded auscultatory record of a rate less than 90 beats per minute till delivery. Features at caesarean section such as amniotic fluid colour, couvellaire uterus, retroplacental clot and its volume were noted.
Neonatal data recorded were—birthweight, Apgar score, cord venous blood pH and base deficit, duration of stay on the neonatal unit, ventilatory support requirement, date and cause of death. For survivors the condition at discharge was documented.
Each of the following variables was examined for a relationship to the outcome: mother's age, parity, gestation, birthweight, time from onset of symptoms to admission, from onset to bradycardia, from bradycardia to delivery and from decision to delivery.
Data were entered in pre-designed datasheets and were entered into a database conforming to the Data Protection Act. Data were analysed using the statistics package SPSS version 10.0.
Data are presented using medians and ranges. The Mann–Whitney U test is used to test for differences between continuous variables grouped by case–control status. Multivariate logistic regression is not used due to small numbers; however, results from univariate logistic analysis are presented.
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Thirty-three cases were identified complying with our criteria. Of these, 11 (33%) had risk factors associated with abruption and 22 (67%) were low risk. Of these 11 women, 3 women had pregnancy-induced hypertension, 2 had pre-eclampsia, 2 were substance abusers and 2 had recurrent small antepartum haemorrhages. Of the remaining two, one was a concealed pregnancy and one had a previous caesarean section.
Specific maternal complications encountered were as follows: five women had minor disorders of coagulation requiring no treatment, one had disseminated intravascular coagulation requiring treatment, one woman had a wound haematoma requiring exploration and one had a postpartum haemorrhage. Women were transfused a mean of 4 units whole blood, ranging from 3 to 8 units. Kleihauer–Bekte test was performed on all women and only one case showed occasional fetal cells.
Follow up information for those surviving to more than one year of age were available in all cases. Eight (24.2%) infants died in the neonatal period. Twenty-two infants (67%) survived and were reported or recorded as developmentally normal at one year of age, and three (12.0%) of the surviving infants have documented cerebral palsy. Two of the normal surviving infants suffered Sudden Infant Death Syndrome in the first year of life. They were thought to be developing normally at the time of death, and have been classified as good outcome. Seven infants were under 32 weeks of gestation. Five survived and are apparently normal, there was one neonatal death, and one survivor has cerebral palsy. Of the 26 infants over 32 weeks of gestation, seven died, and two infants survived with cerebral palsy.
Table 1 shows comparison of outcome in relation to different variables employing Mann–Whitney U test. Although there are substantial differences between the medians for a number of variables, only time from decision to delivery reached statistical significance.
Table 1. Comparison of outcomes in relation to different variables.
| ||Outcome||n||Median||25th–75th centile||Range (min–max)||P*|
|Onset of symptoms to admission||Good||17||60||37.50–157.50||5–1440||0.59|
|Onset of symptoms to onset of bradycardia||Good||17||79||60.00–331.00||5–1551||0.87|
|Onset of bradycardia to decision||Good||22||9||0.75–15.00||0–43||0.11|
|Decision to time of delivery||Good||22||14.5||9.75–22.75||5–37||0.02|
|Onset of bradycardia to time of delivery||Good||21||25.0||16.50–33.50||6–65||0.75|
In order to further determine the relationship between time from decision to delivery and the outcome, we conducted a univariate logistic regression using the outcome of poor (death or cerebral palsy) and good as the dependent variable. Results are presented in Table 2. Based on these results, the odds ratio and 95% confidence interval of a poor outcome for delivery at 20 minutes compared with 30 minutes is 0.44 (0.22–0.86). Given the small sample size, there is no potential to adjust these results for possible confounding variables.
Table 2. Univariate logistic regression.
Figure 1 shows the outcome for 10 minute epochs. Eighty-eight percent of women were delivered within 30 minutes of the recorded decision time, and 55% within 20 minutes.
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Severe placental abruption with fetal bradycardia is associated with poor perinatal outcome. This study shows that speed of response may influence outcome in severe fetal distress. This small study has demonstrated that minimising the length of time from decision to delivery reduced the risk of a poor outcome for the neonate. We were unable to demonstrate a relationship between the duration of bradycardia and outcome—which could be due to small numbers. There was no relationship between the duration of symptoms, gestation or birthweight and outcome.
Maternal morbidity was rare. This may suggest that in well-equipped UK maternity units, concerns about immediate maternal health in this condition should not contribute to delay, although the small sample size advises caution. Throughout the study period the unit had 24 hour dedicated anaesthetic availability, more than one specialist obstetric registrar readily available and rapid access to blood and blood products.
Inferences from the study are limited by its size, the retrospective nature of case ascertainment, and potential for confounding. While it is possible that one or two cases may have been missed, all identifiable records of women delivered with antepartum haemorrhage of any severity in the time period were initially reviewed. We deliberately chose very strict criteria. This led to the exclusion of a number of cases delivered for fetal distress that had severe cardiotocographic changes, including some with short bradycardias that occurred after the decision to deliver on cardiotocographic grounds (n= 60). We felt that these cases introduced heterogeneity, making the decision to deliver less likely to be consistent, and introducing an unquantifiable variable to any examination of outcome. The group was selected to represent as consistent a group as possible, allowing examination of the effect of decision making and organisation on outcome. As a consequence of this rigorous process, the sample size is small, and thus conclusions are less robust.
The relationship between outcome and time in these cases of severe fetal hypoxia from profound and prolonged fetal bradycardia is consistent with animal and other clinical work.
Brann15 suggested that on complete cessation of fetal oxygen supply for a period of 20 minutes, the risk of permanent cerebral damage exceed 50%. According to experimental research in animals, the risk of central nervous system damage would increase in particular among those fetuses whose cerebral perfusion is not increased16,17. This hypothesis is supported by study of patients with premature placental separation whose children as compared with controls demonstrated a fourfold incidence of critical drop in cerebral perfusion5. Information from magnetic resonance imaging of the infant brain has suggested that changes thought typical of hypoxic–ischaemic insults rarely occur if the duration of profound hypoxia is less than 10 minutes, and that profound hypoxia lasting more than 30 minutes is usually associated with death or very severe damage.
In cardiotocographic work, Katz et al.18 examined terminal second stage fetal heart rate traces in otherwise healthy term fetuses, and found a significant increase in metabolic acidosis after 15 minutes. Ingemarrson et al.19 have shown the dramatic rate at which fetal pH can fall following profound bradycardia in the first stage of labour secondary to a number of causes. Other groups have shown increased rates of metabolic acidosis at birth following fetal bradycardia of varying duration20.
Our study is one of the few clinical studies that demonstrate an increase in neonatal morbidity and mortality dependent on the possible duration of insult. Although we were unable to directly link the duration of the bradycardia to outcome, this may be a consequence of the small sample size. A link is inferred from the duration of bradycardia included in the decision to delivery interval.
The National Sentinel Caesarean Section Audit found a median decision to delivery time for cases categorised as ‘immediate threat to the life of the mother or the fetus’ was 27 minutes, and only 25% of such deliveries were achieved within 18 minutes. Recent UK audits have concluded that delivery within 30 minutes may not be possible21,22. Tufnell et al.21 outlined a lengthy list of steps required before emergency caesarean section can be safely mounted. Such a standard has come under increasing criticism for its lack of evidence base23 and there have been calls to provide evidence for support.
However, other groups have taken alternative approaches. Roemer and Heger-Romermann24 in 1993 have critically analysed the structural, logistic and circadian aspect of mounting an emergency caesarean section with the aim of delivering within 20 minutes. The mean time interval observed was: a preparation time of 15 minutes, time of start of surgery until delivery of 4 minutes and a decision to delivery interval of 19 minutes. They then go on to give recommendations for time management in attaining this goal. Wee and Quek25, from Singapore's largest maternity hospital of 15,000 deliveries a year, presented data on a decision to delivery interval of 14.9 minutes, achieved by activation of a ‘code green’ model. Code green is an emergency response signal, which works in a similar fashion to a ‘crash bleep’ but is only activated in specifically identified conditions to which an appointed multidisciplinary team responds. Studies conducted by Hillemanns et al.9 in 1996 in Germany have shown that a mean decision to delivery interval of 12.8 minutes with the 90th centile of 22 minutes is achievable. In the current study, 88% of women were delivered within 30 minutes, and 55% within 20 minutes. It remains to be seen whether the widespread introduction of ‘crash’ caesarean section drills in UK delivery suites will ultimately influence outcome.