Introduction

Globally, Caesarean delivery (CD) rates doubled from 12% in 2000 to 21% ( i.e. 29.7 million births) in 2015. However, evidence exists that 6.2 million CDs are performed annually without medical indications2. While CD can be a life-saving intervention for both the mother and the baby to reduce complications associated with childbirth, it is also performed in situations when neither the mother nor the fetus is at risk of complications. Increasing maternal age at first pregnancy, increasing body mass index (BMI), fetal malpresentation, and repeated CD (women with a previous CD) have been noted as the main factors contributing to the increased CD rate3-5. Although Sweden has one of the lowest CS rates in Europe, the CD rate has also increased over the last two decades from 15.5% in 2000 to almost 18% in 2020, with approximately 83–88% of the total increase accounting for repeat CD6, 7. Due to the increased frequency of CD, studies have been conducted to assess the impact of CD on subsequent pregnancy outcomes8, particularly the risk of stillbirth9, 10 and preterm birth11, 12.
Stillbirth, a baby born with no signs of life, is one of the most common serious adverse pregnancy outcomes. Approximately 2 million babies were stillborn at or after 28 weeks’ gestation in 2019, with a global rate of 13.9 per 1000 births15. In high-income countries (HIC), stillbirth rates vary widely from 1.3 to 8.8 per 1,000 births16. A systematic review and meta-analysis conducted in 2011 to identify important risk factors for stillbirth in HIC reported a 21% increased odds of stillbirth (odds ratio (OR):1.21 [95% confidence interval (CI), 1.07–1.37]) in mothers with a previous CD17. Similarly, a more recent meta-analysis reported a 23% increased odds of stillbirth following CD (pooled OR:1.23 [95% CI, 1.08–1.40])9. Although both reviews reported similar findings, they were limited by high heterogeneity due in part to variation in the cause and timing of stillbirth. A 2020 Norwegian cohort study also reported a slightly higher odds of stillbirth following CD (adjusted OR (aOR):1.45 [95% CI, 1.22–1.73])18, but the authors did not evaluate the impact of the type of CD on the reported associations18. Given the increasing rates of CD, a potential association between CD, specifically unnecessary CD, and subsequent stillbirth is of significant concern.
In pregnancies following a CD, birth can be achieved either by a repeat planned CD, known as elective repeat caesarean section (ERCS) or attempting a vaginal birth, known as vaginal birth after caesarean (VBAC). Limited studies have evaluated perinatal outcomes relating to VBAC18, 19, and evidence on the association between VBAC and stillbirth is lacking and require further investigations. Therefore, we conducted this population-based cohort study to investigate if offspring in deliveries following a previous CD have a higher risk for stillbirth than offspring where the mother had a previous VB. We also examined the risk of stillbirth in women who had a VBAC delivery compared to those who had an ERCS.