Objective To assess the association between obesity and successful vaginal birth after caesarean section (VBAC) in women with different ethnic backgrounds and predict the likelihood of VBAC in this group.

Methods A retrospective cohort study of hospital birth data determined labour outcomes in VBAC candidates. Outcomes were defined as elective repeat caesarean section (ERCS), VBAC and failed trial of labour (TOL). Univariable and multivariable analysis assessed the relationship between ethnic origin and birth outcomes.

Results The cohort included 202 women. Of these, 74 (36.6%) chose ERCS and 128 (63.4%) attempted VBAC. 80 (62.5%) of those women opting for VBAC had vaginal birth and 48 (37.5%) had an emergency caesarean section. The proportion of women choosing VBAC over ERCS was consistent across ethnic groups (>60%), but there was inconsistency in VBAC outcomes between different ethnic groups. Of 47 White women, 32 (68.1%) succeeded in VBAC. Of 65 Black women only 36 (55.4%) were successful. Obesity (body mass index >30 kg/m2) was more prevalent in Black women (30.0% compared to 12.2% in White women). However, of the 22 obese Black women in the cohort, only 40.9% were successful in VBAC compared to 60.0% obese White women.

Conclusions The increasing rate of obesity in the UK is having a negative impact on the number of vaginal births. This study highlights the urgent need to provide women attempting VBAC with individualised risk evaluations, especially in the obese. Further work is required to better quantify this effect in order to improve clinical outcomes.