Definition A caesarean section (CS) is an operation in which a laparotomy (abdominal incision) is undertaken to allow a uterine incision to deliver one or more fetuses, alive or dead after viability (usually 24 weeks’ gestation).

Depending on the urgency, caesarean sections are categorised as follows [1]:

1. 
   

   ◦ Grade 1: For indications that are an immediate threat to the life of the mother or fetus (about 16% of all). In this subgroup of CSs the time taken to achieve delivery will have implications for the risk of fetal morbidity (hypoxic brain injury and possible multi-organ failure in the early neonatal period) and mortality (with a risk of intrapartum demise and stillbirth or death after birth due to the severity of the hypoxic insult). In any situation in which there is a persistent fetal bradycardia or a terminal fetal heart rate pattern (usually swinging deep decelerations with very reduced variability and a slowly falling baseline) the term ‘crash’ caesarean should be used to denote that within Category 1 this is one of the most urgent, in which the whole team needs to pull together, so as to shave valuable minutes off the time it may take to achieve delivery. The underlying pathologies in these situations are usually sudden catastrophic events such as a massive abruption, uterine rupture or a cord occlusion accident such as cord prolapse with pressure on the cord from fetal parts. Perimortem CS done for a woman with cardiac arrest not responding to resuscitation falls within this category, and although not normally described as ‘crash’ also needs to be performed with speed to try to improve outcome. Within this category there are also cases in which there is a high suspicion of established and worsening fetal hypoxia such as pathological (but non-terminal) fetal heart rate patterns or abnormal results from fetal blood sampling or for maternal wellbeing, with the main indication being ongoing antepartum haemorrhage due to placenta praevia where there is concern that ongoing resuscitation is not able to keep pace with the blood loss.

   
   
2. 
   

   ◦ Grade 2: For indications other than maternal or fetal compromise that was not immediately life threatening but where urgent delivery is required (about 32% of all), for example, slow progress in the first stage of labour with a reassuring fetal heart pattern.

   
   
3. 
   

   ◦ Grade 3: For indications where there is a need for early delivery for a fetal or maternal reason but there was no acute compromise (about 18% of all), for example, planned next day delivery for a 34-week fetus with growth restriction and deteriorating Doppler scans. These CSs are often described as ‘semi-planned’.

   
   
4. 
   

   ◦ Grade 4: For non-urgent indications where delivery is timed to suit the mother and the healthcare provider (about 31% of all), for example, pre-labour delivery at 39 weeks for two previous caesarean sections. These CSs are also called ‘elective’ or planned.

There are few recommendations made on time scales for different grades, as even within the grades the exact urgency of the indication is variable. The Royal College of Obstetricians and Gynaecologists (RCOG) advises that the urgency of CS should be considered as a ‘continuum of risk, pointing out that while in some grade 1 indications decision to delivery intervals (DDIs) of as little as 15 minutes can be achieved, studies have shown that this is not invariably the case and also that evidence shows that a DDI of up to 75 minutes is not associated with an increased risk of neonatal compromise compared to shorter a DDI [1]. It also points out that in some cases even delivery within 30 minutes cannot prevent a poor neonatal outcome, adding an argument for the need to treat each case individually. Overall, they conclude that the urgency of CS should be individualised based on the risk to the fetus and the safety of the mother. They recommend that in cases of acute fetal compromise a target DDI of 30 minutes is used but with the caveat that in some cases delivery needs to be undertaken even more rapidly to try to reduce the risk of a poor outcome. The term ‘crash’ caesarean should be reserved for those cases as described that are truly time critical where all efforts need to be made so that the DDI will be as quick as possible without compromising maternal safety.

Incidence The World Health Organisation long-standing recommendation is that the total CS rates (combination of elective and emergency procedures) should be 10%–15%, commenting that on a population basis higher rates of CS do not appear to be associated with reduction in maternal and neonatal mortality rates. They also acknowledge that these rates are not being achieved, with most developed countries reporting CS rates well in excess of these levels and have recommended the use of the Robson classification system in order to allow CS rates to be compared globally over time [2]. There is no global evidence on the rates of emergency versus elective type CS and what optimal rates might be expected. Of note, the indications for ‘crash’ CS are almost never open to dispute such that the expected rates of CS within this category should depend only on the incidence of these conditions and the availability of a healthcare system to undertake the operation. There are no prospective studies that have assessed what the optimal rate of CS should be, but it would seem reasonable to assume that it would vary significantly depending on population demographics. However, a number of recent studies have reviewed data on global CS rates and used mathematical modelling to assess the association between CS rates and maternal, neonatal and infant mortality/morbidity; a systematic review of these ecologic type studies concluded that CS rates above a threshold of 9%–16% are not associated with decreases in mortality even where adjustments for socio-economic factors are made [3]. A retrospective analysis of mode of delivery data for 2010 from 31 European countries showed wide variation in CS rates, with the highest total rate seen in Cyprus (52.2% due to a 38.8% rate of planned CS) and the lowest 14.8% in Iceland; the lowest rate of emergency CS was seen in Sweden, where only 8.6% of women required delivery by emergency CS. The rate of emergency CS in all four countries of the United Kingdom was similar at about 15%, with an elective rate showing more variability, 9.9% (England) to14.6% (Northern Ireland), resulting in an overall CS rate of 24.6% (England) to 29.9% (Northern Ireland) [4].