1-Supraphysiological estrogen levels attained during ovarian stimulation|
2-Medications used during ovarian stimulation:
•GnRH analogues: agonists & antagonists
•HCG used to trigger ovulation
3-Other probable causes: abnormal levels of other hormones, peptides and local autocrine mediators associated with ovarian stimulation
5-Maternal endocrine system: ovaries (corpus luteum), pituitary gland and hypothalamus.
6-Other probable targets e.g.
•Early developing placenta