OHSS and ART: Why some and not others?

Alpha(2)-macroglobulin (alpha(2)M) is a multifactorial binding protein that may be a naturally occurring inhibitor of VEGF. High concentrations in follicular fluid may be necessary to allow formation of the corpus luteum. The aim of this work was to determine if there is a relationship between serum VEGF levels, alpha(2)M levels and the development of OHSS in hyperstimulated subjects (>15 oocytes). Venous blood was collected at the time of oocyte retrieval (OR) from 52 subjects. There was no statistically significant difference in serum VEGF levels at the time of OR between hyperstimulated subjects who did and did not develop OHSS. By contrast, the serum level of alpha(2)M was statistically, significantly higher in the group of subjects who did not develop OHSS. These results suggest that elevated alpha(2)M levels are associated with a decreased risk of developing OHSS. Alpha(2)M may act as a 'removing and inactivating' protein for VEGF, higher levels acting as a protectant against the syndrome.