Main findings
Outpatient-balloon IOL is cost-saving with lower costs and better health outcomes than inpatient-PG IOL. The robustness of these findings was tested through sensitivity analyses varying the costs of CS, and the mean hourly costs in antenatal ward, birth suite, postnatal ward, and neonatal nurseries. In all tested scenarios, outpatient-balloon IOL was favoured, with consistently higher NMB and an ICER below the WTP threshold. Although outpatient-balloon IOL had a higher mean NMB and lower cost/QALY gained these results are not conclusive that outpatient-balloon IOL is the preferred alternative for all women. Indeed, the probabilistic sensitivity analyses showed outpatient-balloon IOL was cost-effective 55.3% of the time. The subgroup analyses by parity, however, more strongly indicated cost-effectiveness of outpatient-balloon IOL for nulliparous women (NMB $28,420 vs $25,675) and inpatient-PG IOL for parous women (NMB $36,969 vs $34,210). Subgroup analysis by cervix favourability was surrounded by higher levels of uncertainty.
The difference in cost outcomes between the two methods of IOL was largely due to the amount of time spent in the antenatal ward. Outpatient-balloon IOL was associated with a saving of almost 13 hours in antenatal ward care and, consequently, the mean costs were more than six times higher in the inpatient-PG group ($781 vs $129). Furthermore, cervical priming costs in the balloon group were less than half that of the PG group ($49 vs $105). The mean length of stays in birth suite and in the postnatal ward were slightly longer in the balloon group (~1.5hrs) which may reflect the higher proportion of nulliparous women in this group (72.7% vs 67.1%), who typically experience a longer labour and longer postnatal stay than parous women. Whilst acknowledging the inherent difficulties in costing each hour of care in each clinical unit, these findings highlight the importance of considering location and not just the duration of care when designing cost-effective models of care. Our findings from a health services perspective suggest that using outpatient-balloon IOL is expected to be cost-saving, especially for nulliparous women. In practical terms cervical priming costs will be reduced and less time spent in antenatal wards is expected to reduce costs as well as free up both hospital beds and staff time. The actual impact within health services might differ between facilities and should be further explored in future studies.