In which phase do the primary oocytes get arrested during early foetal development?
Prophase of Meiosis I
Oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each foetal ovary; no more oogonia are formed and added after birth. These cells start division and enter into prophase-I of the meiotic division and get temporarily arrested at that stage, and are called primary oocytes. They remain arrested at this phase until puberty, after which monthly changes happen.