Since every woman’s menstrual cycle is different, the standard of her lining and follicles at day 12 of her period can vary greatly. For women who usually have a regular menstrual cycle of 28-30 days, the thickness of the lining is usually around 4-6mm and the standard of the follicle is around 1.5cm on the 12th day of menstruation. However, if a woman’s menstrual cycle is usually pushed forward, then ovulation may have already occurred by the 12th day of menstruation, so the thickness of the lining at this time may be 6-8mm, and the follicle may be around 2-2.3mm, or even the follicle may have already been discharged from the ovary. For women with irregular menstrual cycles that are pushed back, the lining may still be at 4mm on day 12 of menstruation and the follicle may still be less than 1cm or less.