The formation of mature female gametes is called oogenesis.
This process starts during embryonic development in the mother's womb.
The gamete mother cells called oogonia are formed within the fetal ovary.
The oogonia undergo mitotic division to form a primary oocyte.
Primary oocyte:
The primary oocytes are produced during the embryonic stage by oogenesis.
At the embryonic stage, each oogonium inside the ovary of a fetus divides by mitosis to form a primary oocyte which enters the prophase of meiosis I and gets arrested at this phase of the cell cycle, until the child reaches the puberty age.
At the puberty stage, the primary oocyte will complete meiosis I to form a secondary oocyte.