This study examines the relationship among prenatal maternal stress, sleep quality and unplanned Caesarean delivery. For this research, we adopted a prospective survey design and a sample of 200 women in the early stages of labour. The findings were as follows: (i) 11.5% of the participants underwent unplanned Caesarean sections; (ii) based on a Pittsburg Sleep Quality Index split point of 5, approximately 90.5% of the participants experienced poor sleep quality; and (iii) the odds ratio for primiparas undergoing an unplanned Caesarean section was 4.183 times that for multiparas (95% confidence interval (CI) = 1.177 to 14.864), indicating a statistically significant difference. The results also showed that stress was a significant factor related to unplanned Caesarean sections; a 1-point increase on the Pregnancy Stress Rating Scale was associated with a 1.033-fold higher probability of undergoing an unplanned Caesarean section (95% CI = 1.002 to 1.065). Furthermore, prenatal stress was a significant variable that can be used to predict unplanned Caesarean deliveries.