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Woman's pregnant stomach

A large study of women who have had one or more previous caesarean sections suggests that attempting a vaginal birth in a next pregnancy is associated with higher health risks to both the mother and the infant than electing for another caesarean. However, the absolute risk of complications is small for either type of delivery. 

The research, published in the open access journal PLOS Medicine on September 24 and funded by the National Institute for Health Research (NIHR), addresses a lack of robust information on the outcomes of birth options after previous caesarean section. Kathryn Fitzpatrick who led the study said ‘Our findings can be used to counsel and manage women with previous caesarean section and should be considered alongside existing evidence on the increased risk of serious maternal morbidity in subsequent pregnancies associated with elective repeat caesarean section’. 

Around the world there have been increases in caesarean section deliveries, leading to a larger proportion of pregnant women with a history of caesarean section. Guidelines recommend that these women be counselled about the benefits and harms of planning a subsequent caesarean or attempting a vaginal birth yet there is little evidence around this. 

Kathryn Fitzpatrick and colleagues used data from 74,043 full term births of single babies in Scotland between 2002 and 2015. For women who have had previous caesarean section, the researchers estimated the short term maternal and perinatal health outcomes associated with attempting a vaginal birth compared to planning another caesarean section. 45,579 women gave birth by planned caesarean and 28,464 attempted vaginal birth, 28.4% of whom went on to have an emergency caesarean section. 

Attempting vaginal birth was associated with an increased risk of the mother having serious birth and post-birth related problems compared to electing for another caesarean section. Attempting vaginal birth was more likely to result in uterine rupture (69 vs 17 women, adjusted odds ratio [aOR] 7.3, 95% confidence interval [CI] 3.9–13.9), a blood transfusion (324 vs 226 women, aOR 2.3, 95% CI 1.9–2.8), sepsis (76 vs 78 women, aOR 1.8, 95% CI 1.3–2.7 ), surgical injury (aOR 3.0, 95% CI 1.8–4.8), and more serious infant outcomes such as intrapartum stillbirth or neonatal death, admission to neonatal unit, resuscitation requiring drugs or intubation, or an Apgar score less than seven at five minutes (2,049 vs 2,570).  

However, attempting vaginal birth was associated with increased likelihood of breastfeeding, whereas the risk of other maternal outcomes varied according to a woman’s previous pregnancy history. For example, a woman’s risk of having a post-birth hospital stay greater than 5 days was reduced in those attempting vaginal birth compared to those planning another caesarean only if they had any prior vaginal births. 

It should be noted that the absolute risk of complications were small for either type of delivery. Overall, just 1.8% of those attempting a vaginal birth and 0.8% of those having a planned caesarean experienced serious maternal complications. 8.0% of those attempting a vaginal birth and 6.4% of those having a planned caesarean had one or more of the adverse infant outcomes examined. 

Further studies are needed to replicate these findings and investigate the longer-term outcomes besides the well-known risk of serious maternal complications in future pregnancies associated with multiple caesareans.