Association between hospital treatment volume and major complications in ovarian hyperstimulation syndrome

Objective: An inverse relationship between hospital volume and adverse patient outcomes has been established for many conditions, but has not yet been examined in ovarian hyperstimulation syndrome (OHSS). Given the rarity of severe OHSS, but potential for high morbidity, this study aimed to elucidate the effect of hospital volume on inpatient OHSS-related complications.

Methods: This is a retrospective observational study querying the National Inpatient Sample, 1/2001-12/2011. Study population was 11,878 patients with OHSS treated at 735 hospitals. Annualized hospital OHSS treatment volume was grouped as: low-volume (1 case/year), mid-volume (>1 but < 3.5 cases/year), and high-volume (≥3.5 cases/year). Main outcome measure was major complication rates stratified by hospital treatment volume, assessed by multinomial regression and binary logistic regression models.

Results: A total of 2,415 (20.3%) patients were treated at low-volume centers, 5,023 (42.3%) at mid-volume centers, and 4,440 (37.4%) at high-volume centers. Patients treated at high-volume centers were more likely to be older and less comorbid with higher incomes and lower body mass index (P < 0.05). High-volume hospitals were more likely to be urban-teaching centers with large bed capacity (P < 0.001). Overall, 1,624 (13.7%) patients experienced a major complication during hospitalization. Patients treated at high-volume hospitals had lower rates of major complications (high: 11.0%, mid: 15.2%, low: 15.6%, P < 0.001). On multivariable analysis, treatment at high-volume hospitals was independently associated with a nearly 20% lower rate of major complications (odds ratio 0.82, 95% confidence interval 0.70-0.97, P = 0.021).

Conclusion: Our study suggests that higher hospital treatment volume for OHSS may be associated with improved outcomes.