Emergency caesarean section is required when delivery can reduce the risk to the life of the mother or foetus. When a caesarean section is indicated for foetal compromise, a decision-to-delivery interval of 30 min (or less) has been suggested as the ideal time frame within which an obstetric team should achieve delivery. In theory, a short decision-to-delivery interval may minimise intra-uterine hypoxia and improve neonatal outcome. Current medical evidence does not support this time frame. There are certain indications for caesarean section that necessitate a much shorter decision-to-delivery interval, but evidence suggests that the majority of neonates may be safely delivered within a longer interval of time. Current tools available for the diagnosis of foetal distress are imperfect, and the concept of foetal distress is poorly defined. Future research should focus on finding accurate means of diagnosing foetal distress in labouring women and establishing universally agreed evidence-based decision-to-delivery targets without compromising maternal or foetal safety.
What does urgency mean for caesarean section?
Emergency caesarean section is required when delivery can reduce the risk to the life of the mother or foetus. When a caesarean section is indicated for foetal compromise, a decision-to-delivery interval (DDI) of 30 min (or less) has been suggested as the ideal time frame within which an obstetric team should achieve delivery to minimise hypoxic ischaemic morbidity. However, the origin and evidence base for this time frame are unclear. Literature suggests that the figure of 30 min originated from animal models in the 1960s or that is was derived from the United States survey data that sought to explore the minimal time required by obstetric units to safely perform a caesarean section . An important consideration when evaluating the appropriate DDI is the recognition that there is considerable variation in the degree of urgency of non-elective caesarean section. Caesarean sections may be classified as either elective, referring to any planned caesarean delivery, or emergency, referring to everything else. Therefore, a wide range of indications for ‘emergency’ caesarean section exists, with huge variability in the actual clinical urgency of delivery; for example, ‘emergency’ could describe a situation where cord prolapse leading to foetal bradycardia has occurred or a woman who requires caesarean delivery because of delay in the first stage of labour. The description of a modified four-point classification of urgency, endorsed by the Royal College of Obstetricians and Gynaecologists (RCOG) ( Table 1 ), has sought to improve clarity for clinicians and thus communication between labour ward team members. Clarification regarding the natures of non-elective caesarean deliveries being performed in a single unit would additionally enhance the quality of data collection for local and national audit . The original four-point classification proposed by the RCOG incorporates a colour scale (red to green) to reinforce the need to recognise that a ‘continuum of urgency’ applies to caesarean section, rather than distinct categories.
| Category | Definition |
|---|---|
| 1. Emergency | Immediate threat to woman or foetus |
| 2. Urgent | Maternal of foetal compromise that is not immediately life threatening |
| 3. Scheduled | Needing early delivery but no maternal or foetal compromise |
| 4. Elective | At a time to suit the woman and maternity team |
What is the current evidence for a 30-min time frame?
There is little, if any, evidence and no randomised controlled trial to support that a DDI of 30 min results in a better outcome for the mother or neonate. The majority of the evidence is linked to observational data.
Tuffnell et al. described the results of a 7-year continuous audit of emergency caesarean sections and assessed the relationship between DDI and admission to the neonatal special care unit. In this audit, the DDI did not significantly correlate with admission rates for babies born at 36 weeks’ gestational age or older . MacKenzie published the results of a smaller prospective observational study of 100 emergency caesarean sections, exploring the association between DDI and outcome . Umbilical cord pH, as an assessment of foetal well-being, measurements had improved in those deliveries with a longer DDI. These findings highlight two points that emphasise the difficulty of research in this area. First, the use of umbilical cord pH as marker for foetal outcome: there are no long-term studies investigating the association of umbilical cord pH with long-term outcome. Second, a reduced pH may occur in faster/rushed deliveries because of anxiety-induced maternal catecholamine release, resulting in reduced perfusion to the placental bed.
The UK National Sentinel Caesarean Section audit is one of the largest projects ever to have studied this subject. They assessed 17 780 births by emergency caesarean section over the course of a 2-month period . The association between DDI (divided into 15-min intervals) and outcome (Apgar scores at 5 min and stillbirths) was investigated. The authors found that babies delivered within a DDI of 15 min or less showed no improvement in outcome compared with those born within DDIs of 16–75 min. Beyond 75 min, there was a significant decrease in Apgar scores at 5 min and significant increase in mothers requiring an increased level of postoperative care.
A prospective observational cohort study of over 500 women who underwent unplanned caesarean delivery mapped the DDI and neonatal condition. The authors found that the risk of neonatal acidosis was not reduced by delivery within 30 min for Category 1 caesarean sections (OR 0.56; 0.11–2.81) or within 75 min for Category 2 (OR 2.72; 0.6–25.1).
A systematic review published in 2014(9) sought to determine how frequently a 30 min DDI was achieved in emergency caesarean section and whether achieving a 30 min DDI resulted in a significant alteration in neonatal outcome. The study included 34 studies reporting on 22 936 women (all were observational studies); 13 of the studies reported one or more neonatal outcomes for deliveries achieved within 30 min of the decision compared to those where delivery occurred more than 30 min from the decision. The authors found that where delivery was achieved within 30 min of the decision, babies were more likely to have Apgar scores of <7 (OR 3.1) and an arterial cord pH of <7.1 (OR 3.4); however, when this association was studied in Category 1 caesarean sections only, no statistically different neonatal outcomes (5-min Apgar score of <7 and umbilical artery pH < 7.10) were demonstrated. The authors did comment that this subgroup analysis included only a very small number of studies. Finally, this analysis found there was no association between the speed of delivery and admission to a neonatal special care unit.
While this analysis found that there was no convincing evidence to suggest that DDIs of greater than 30 min were associated with worse neonatal outcomes, it did highlight another important factor. In studies that analyse ‘emergency’ caesarean sections, there is considerable heterogeneity in the clinical reasons that necessitate caesarean delivery, e.g. the inclusion of cases of cord prolapse with cases of labour delay. It would be potentially more useful to examine the effect of DDIs by focussing on one irreversible indication for emergency delivery, e.g. uterine rupture. Indeed, in one small study examining the relationship between DDI and neonatal outcome in uterine rupture, poor neonatal outcomes were found with DDIs of >18 min .
Table 2 summarises some of the existing evidence regarding the effect of a 30-min DDI on perinatal outcome.
| Author | Year of publication | Country | No of cases | Retrospective/prospective | Outcome measured | Result |
|---|---|---|---|---|---|---|
| Bello et al. | 2015 | Nigeria | 235 | Prospective | 5-min Apgar score Admission to NSCU Perinatal mortality | No significant association found. |
| Berlit et al. | 2013 | Germany | 336 | Retrospective | Umbilical cord arterial pH and base excess Apgar score at 5 min | DDI had no effect on outcome (although all deliveries were performed within a 20-min DDI) |
| Bloom et al. | 2006 | USA | 2808 | Prospective | Admission to NSCU Hypoxic ischemic encephalopathy Seizures Cardiopulmonary resuscitation Arterial or venous cord pH 5-min Apgar score Maternal complications | DDI <30 min associated with greater neonatal acidaemia and higher rates of endotracheal intubation in the delivery suite. No association with maternal outcome shown. |
| Harfouche et al. | 2015 | Malawi | 513 | Prospective | Maternal morbidity and neonatal mortality | No association with DDI |
| Hillemans et al. | 2005 | Germany | 109 | Retrospective | Umbilical artery pH Apgar scores | All deliveries occurred within 30 min in the delivery room. DDI ≤20 min were associated with lower Apgar scores. |
| Holcroft et al. | 2005 | USA | 117 | Retrospective | Umbilical artery pH | Shorter DDIs were associated with lower umbilical artery pH |
| Huissoud et al. | 2010 | France | 666 | Prospective | 5-min Apgar score Umbilical artery pH CPR Intubation Respiratory distress Early neonatal death | No significant correlation between 30-min DDI and outcome |
| MacKenzie et al. | 2001 | England | 415 | Prospective | Umbilical arterial pH | Less acidaemia with longer DDI |
| Nasrallah et al. | 2004 | USA | 111 | Retrospective | Apgar scores at 1, 5 and 10 min umbilical cord blood gases admission to NSCU length of stay neurological injury Maternal complications | No statistically significant association in DDI <30 min and outcome |
| Onah et al. | 2005 | Nigeria | 224 | Prospective | 1- and 5-min Apgar scores Admission to NSCU perinatal death | No association DDI and adverse neonatal outcome |
| Oppong et al. | 2014 | Ghana | 495 | Retrospective | 5-min Apgar score Admission to NSCU | Increased risk of neonatal mortality if DDI >1 h (Category 1 indication) or >2 h (Category 2 indication) |
| Pearson et al. | 2011 | England | 546 | Prospective | 1- and 5-min Apgar cord pH and cord BE long-term disability | No association between DDI and long term disability, shorter DDIs associated with greater acidosis |
| Roy et al. | 2008 | India | 217 | Prospective | 5-min Apgar score umbilical cord pH Artificial ventilation Admissions to NSCU | DDI ≤30 min associated with increased rate of NSCU admissions |
| Thomas et al. | 2004 | England | 17780 | Prospective | 5-min Apgar score Maternal adverse outcome | No association if DDI <75 min Higher odds of a five minute Apgar score of <7 in DDI >75 min and 50% increase in odds of special for mothers |
| Tuffnell et al. | 2001 | England | 721 | prospective | Admission to NSCU | No association between DDI and NSCU if born at ≥36/40 |
What is the current evidence for a 30-min time frame?
There is little, if any, evidence and no randomised controlled trial to support that a DDI of 30 min results in a better outcome for the mother or neonate. The majority of the evidence is linked to observational data.
Tuffnell et al. described the results of a 7-year continuous audit of emergency caesarean sections and assessed the relationship between DDI and admission to the neonatal special care unit. In this audit, the DDI did not significantly correlate with admission rates for babies born at 36 weeks’ gestational age or older . MacKenzie published the results of a smaller prospective observational study of 100 emergency caesarean sections, exploring the association between DDI and outcome . Umbilical cord pH, as an assessment of foetal well-being, measurements had improved in those deliveries with a longer DDI. These findings highlight two points that emphasise the difficulty of research in this area. First, the use of umbilical cord pH as marker for foetal outcome: there are no long-term studies investigating the association of umbilical cord pH with long-term outcome. Second, a reduced pH may occur in faster/rushed deliveries because of anxiety-induced maternal catecholamine release, resulting in reduced perfusion to the placental bed.
The UK National Sentinel Caesarean Section audit is one of the largest projects ever to have studied this subject. They assessed 17 780 births by emergency caesarean section over the course of a 2-month period . The association between DDI (divided into 15-min intervals) and outcome (Apgar scores at 5 min and stillbirths) was investigated. The authors found that babies delivered within a DDI of 15 min or less showed no improvement in outcome compared with those born within DDIs of 16–75 min. Beyond 75 min, there was a significant decrease in Apgar scores at 5 min and significant increase in mothers requiring an increased level of postoperative care.
A prospective observational cohort study of over 500 women who underwent unplanned caesarean delivery mapped the DDI and neonatal condition. The authors found that the risk of neonatal acidosis was not reduced by delivery within 30 min for Category 1 caesarean sections (OR 0.56; 0.11–2.81) or within 75 min for Category 2 (OR 2.72; 0.6–25.1).
A systematic review published in 2014(9) sought to determine how frequently a 30 min DDI was achieved in emergency caesarean section and whether achieving a 30 min DDI resulted in a significant alteration in neonatal outcome. The study included 34 studies reporting on 22 936 women (all were observational studies); 13 of the studies reported one or more neonatal outcomes for deliveries achieved within 30 min of the decision compared to those where delivery occurred more than 30 min from the decision. The authors found that where delivery was achieved within 30 min of the decision, babies were more likely to have Apgar scores of <7 (OR 3.1) and an arterial cord pH of <7.1 (OR 3.4); however, when this association was studied in Category 1 caesarean sections only, no statistically different neonatal outcomes (5-min Apgar score of <7 and umbilical artery pH < 7.10) were demonstrated. The authors did comment that this subgroup analysis included only a very small number of studies. Finally, this analysis found there was no association between the speed of delivery and admission to a neonatal special care unit.
While this analysis found that there was no convincing evidence to suggest that DDIs of greater than 30 min were associated with worse neonatal outcomes, it did highlight another important factor. In studies that analyse ‘emergency’ caesarean sections, there is considerable heterogeneity in the clinical reasons that necessitate caesarean delivery, e.g. the inclusion of cases of cord prolapse with cases of labour delay. It would be potentially more useful to examine the effect of DDIs by focussing on one irreversible indication for emergency delivery, e.g. uterine rupture. Indeed, in one small study examining the relationship between DDI and neonatal outcome in uterine rupture, poor neonatal outcomes were found with DDIs of >18 min .
Table 2 summarises some of the existing evidence regarding the effect of a 30-min DDI on perinatal outcome.
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