Hi. Thanks for your query and for using Health Care Magic
Ovarian Cysts are are of two major types.
1. Physiological - these from in ovaries during normal menstrual cycle (called Dominant Follicle) and rupture soon after ovulation. Such cysts usually rupture/regress soon after ovulation i.e 14 days after last menstrual period for 20 days cycle.
2. Pathological (Benign and Malignant)- These are cysts which grow out of the surface epithelial cells
and some gradually enlarge. The are not related to menstruation
and therefore do not rupture or regress with mensturation.
Your nephew's ultrasound
report will tell you clearly whether its a follicular cyst
(which usually regresses) or otherwise.
Hope this answers your query.
Do get back if you need more information
Thanks and Regards