DO THE RIGHT AND LEFT OVARIES RESPOND EQUALLY DURING CONTROLLED OVARIAN STIMULATION?

Abstract

Anatomical and cyclical differences exist between the left (LO) and right ovary (RO). For example, the RO has more “efficient” vascularization as it drains directly into the inferior vena cava, whereas the LO first drains to the left renal vein. Differences in response between the LO and RO during controlled ovarian stimulation (COS) have been less well-studied. The goals of this study were to evaluate COS response according to ovarian laterality by assessing follicular count on the day of trigger and to determine patient-specific variables associated with laterality response. This was a retrospective study of all patients who underwent COS resulting in egg retrieval between 10/2019 – 9/2020 at an academic fertility center. The number of follicles >10mm on the day of trigger from the RO vs. LO were measured. Patient variables including AMH, BMI and age were collected. Cycles were stratified into 3 groups: equal follicular count documented on both sides (R=L), more follicles documented on right (R>L), and more follicles documented on left (L>R). Patients with only a 1 or 2 follicular difference were excluded from the R>L and L<R groups. ANOVA and linear regression models were performed to compare the three groups and to determine the relationship between AMH, BMI, and age with laterality. There were 261 cycles that met study criteria. Eighty-six (32.9%) cycles had R=L, 106 (40.6%) had R>L (difference range: ≥3-10), and 69 (26.4%) had L>R. Those with R>L were younger than the other groups (p=.04). There was no significant difference in AMH or BMI between the 3 groups overall (Table). Higher AMH was associated with having more follicles on R>L (p=.02). Increasing age was associated with L>R (p=.01). BMI was not associated with laterality response. Higher AMH and younger age are associated with more measured follicles on the right vs. left ovary during COS. This aligns with established data that the RO is more active during the younger reproductive years, with a transition to the LO during the later phase of reproductive life.