OHSS is a series of symptoms caused by excessive ovarian responses to exogenous gonadotropins. Its specific pathogenesis is unclear and possibly includes increased capillary permeability, decreased perfusion of essential organs, electrolyte disturbance, and blood concentration . The clinical manifestations are bilateral ovarian enlargement, pleural ascites, abdominal distension, liver and kidney dysfunctions, and other serious complications. VEGF, due to its angiogenic properties, is currently considered a critical factor for the occurrence of OHSS . The risk factors for OHSS include age < 35 years, polycystic ovary syndrome or polycystic ovarian changes, BMI < 18.5 or > 24, anti-Müllerian hormone (AMH) > 3.36 ng/mL, increased number of sinus follicles (increased AFC is also a sensitive predictor for OHSS), increased follicular development and oocyte retrieval numbers, and OHSS history in the former cycles.
A study showed that the OHSS risks for young infertile patients aged < 35 years were higher than those for patients aged > 35 years . Danninger et al.  followed 101 patients with IVF-assisted pregnancy and found that patients with OHSS had a significantly lower BMI than those without OHSS. AMH can identify ovarian reactivity to exogenous gonadotropins during the ovulation cycle. Lee et al.  found that AMH was a predictor of OHSS when it was higher than 3.36 ng/mL. Jayaprakasan et al.  and other researchers  have shown that the greater the number of AFCs for infertile patients, the higher the incidence and risks of moderate to severe OHSS. Thus, this retrospective study evaluated if combined treatment with prednisone and bromocriptine is better than single-treatment with bromocriptine for OHSS prevention and whether it will influence pregnancy outcomes. Some differences in gonadotropin duration and endometrial thickness on trigger day were found between the two groups (Table 2). Although the gonadotropin duration was different, which led to different progesterone and LH levels on the trigger day, the gonadotropin doses and E2 levels were not statistically different between the two groups. Based on the OHSS diagnostic standard, some patients in this study only had symptoms of mild OHSS in some cycles, while a few others experienced no symptoms of abdominal distension, discomfort, mild nausea/vomiting, or diarrhea and only showed an increased E2 level.
The significant difference in the OHSS cancellation rate (31.50% in the combined-treatment group and 40.88% in the single-treatment group) indicated that combined treatment with prednisone and bromocriptine was better than bromocriptine alone for relieving OHSS and also for dramatically decreasing the cancellation rate for the fresh embryo transfer cycle. Also, there was no statistical difference in the proportion of the controlled ovarian stimulation protocol between these two groups, which mainly existed in the agonist protocols, but the antagonist protocols were in the minority. Analysis of embryo quality and embryo transfer outcome indicated that the combination of bromocriptine and prednisone can relieve the symptoms of OHSS but would not influence the quality of the transferred embryos.
Regarding pregnancy outcomes, there were no statistical differences in clinical pregnancy, ongoing pregnancy, live birth, and early miscarriage rates between the two groups. Although the cycles of the single-treatment group to which only one embryo was transferred were fewer than those of the combined-treatment group, the implantation rate in the combined-treatment group was significantly better than that in the single-treatment group. This demonstrated that the advantages of selective embryo transfer and the pregnancy outcome may be closely related to the embryo quality itself and have little to do with the number of embryo transfers. Although fetal malformation occurred in five cycles in the combined-treatment group and three cycles in the single-treatment group (including congenital heart disease, six-finger deformity, and abdominal fissure malformation), there was no significant difference in the incidence of fetal malformation and ectopic pregnancy between the two groups. Furthermore, there were no significant statistical differences in the rates of biochemical pregnancy and congenital disabilities between the combined- and single-treatment groups. This led us to believe that when used in combination as an intervention for susceptible patients (that lead to OHSS during the controlled ovarian stimulation medication), both had no influence the pregnancy outcome even for the malformation or some congenital disease and also showed no side effects.
This study has a few limitations. Since this is a retrospective study, all relevant data were not randomized. Therefore, randomized experimental research will have to be designed to obtain more reliable results to confirm whether prednisone combined with bromocriptine could have a better effect on OHSS prevention in fresh transfer cycles. We should also design a new group study for patients with a high responder and for a normal responder to make sure if these combined treatments would have different effects on diverse groups of patients.