<prompt> Ovulation occurs :Before LH surgeAfter biphasic rise in body temperatureAfter ripening of follicle by FSHBefore estrogen peak  <response>: Ovulation After estradiol reaches a peak of 200pgml and is sustained for about 48 hours, it exes a possitive feedback action for LH surge Final maturation of follicle is obtained by combined effect of FSH and LH Ovulation occurs 24-48 hours after LH surge Ref: D.C. Duttas Textbook of Gynaecology, 6th edition, page no: 93 