Clinical practice guidelines recommend the active management of the third stage of labour, but it is currently unknown what practices professionals actually perform. Therefore, the aim of this study was to determine the variability of professional practices in the management of the third stage of labour and to identify any associated professional and work environment factors. A nationwide cross-sectional study was performed with 1054 obstetrics professionals between September and November 2018 in Spain. A self-designed questionnaire was administered online. The crude odds ratios (OR) and adjusted odds ratios (ORa) were estimated using binary logistic regression. The main outcome measures were included in the clinical management of the third stage of labour and they were: type of management, drugs, doses, routes of administration, and waiting times used. The results showed that 75.3% (783) of the professionals used uterotonic agents for delivery. Oxytocin was the most commonly administered drug. Professionals who attend home births were less likely to use uterotonics (ORa: 0.23; 95% confidence interval (CI): 0.12–0.47), while those who completed their training after 2007 (ORa: 1.57 (95% CI: 1.13–2.18) and worked in a hospital that attended >4000 births per year (ORa: 7.95 CI: 4.02–15.72) were more likely to use them. Statistically significant differences were also observed between midwives and gynaecologists as for the clinical management of this stage of labour (p < 0.005). These findings could suggest that there is clinical variability among obstetrics professionals regarding the management of delivery. Part of this variability can be attributed to professional and work environment factors.