The follicles are mature before they can ovulate and conception can occur after ovulation. The normal size of a mature follicle is 18-25mm, if it is larger or smaller than this range it will lead to non-ovulation and affect conception. During ovulation, you need to go to the hospital regularly to check the development of the follicles, which can grow 0.2cm per day and can be monitored by ultrasound. If you find that the follicles are slow to develop or not developing, it may be caused by a lack of estrogen in your body. You can have a hormone 6 test and take Deferiprone tablets for regulation to promote follicle development. You can also use ovulation medication such as Clomiphene to promote follicle development and arrange intercourse when the follicles reach about 20mm to improve the chances of conception.