Investigation on the risk factors for late-onset OHSS: a retrospective case-control study

The pathophysiology of ovarian hyperstimulation syndrome (OHSS) is largely unknown. High ovarian response is acknowledged as a risk factor. However, in our clinical practice, the incidence of OHSS is not necessarily linked to the degree of such response among women. Here, we aimed to screen for potential risk factors other than those associated with ovarian response.

A total of 21,222 ovarian stimulation cycles were collected among women undergoing assisted reproductive technology, among which 84 patients with late-onset OHSS were identified as cases; corresponding matched control cases were obtained from the remaining 21,138 cycles. A multivariable logistic regression with the best subset method was performed to screen for significant risk factors.

First, control samples were obtained with a case-to-control ratio of 1:4. The matching criteria were mainly ovarian response-related factors including age, body mass index, number of oocytes retrieved, standard or mild ovarian stimulation, and specific ovarian stimulation protocols. After matching the five ovarian response-related factors, 81 cases and 318 controls were obtained. The best model was selected after analysis as above. Basal serum low-density lipoprotein cholesterol (LDL-C), basal total cholesterol (TC), and estradiol (E₂) concentrations on the day of triggering ovulation were included in the model, with odds ratios of 0.3410 (95% confidence interval, CI, 0.1618-0.7186), 2.2008 (95% CI 1.1192-4.3275) and 1.0000 (95% CI 1.0000-1.0001), respectively.

Basal LDL-C was a risk factor negatively associated with late-onset OHSS, while basal TC and triggering E₂ levels during ovarian stimulation were positive risk factors.