The primary and secondary oocytes are suspended in prophase I and metaphase II respectively due to secretions from the
Granulosa cells
The primordial ovum gets surrounded by spindle shaped cells from the stroma of the ovary, which differentiate to form circular granulosa cells. These cells provide nourishment to the ovum. This primordial ovum along with a single layer of granulosa cells is called the primary follicle. The primordial ovum enclosed within the primary follicle begins meiosis, but the process is paused at prophase 1 of the first meiotic division by secretions of the granulosa cells that freeze the ovum in this state. During each ovarian cycle the secondary oocyte formed is also arrested at meiosis II due to the secretions of the granulosa cells.