Vishnu keeps taking avatar from time to time . Does he take birth from women's womb like normal humans do. Or Does he take avatar outside of womb i.e. he appears outside of the womb ?
Well, Lord Vishnu takes birth from human womb.
Srimad Devi Bhagwatam MahaPuranam 5:1:12-54. says thus.:
12-54. Vyāsa said :-- "........ O king! Brahmā, Viṣṇu and Śiva are sprung respectively from the Rājasic, Sāttvic, and Tāmasic Ahamkāras. In these three, the three Ahamkāras are always to be found, so the Munis, that have realised the Real Essence, declare. They are all bound by this Ahamkāra; there is no doubt in this. The Pundits of dull intellect, and deluded by Māyā declare that Viṣṇu takes various incarnations out of his own free will; for when it is seen that men of even inferior intellects do not entertain any desire to enter into the wombs, painful and terrible; how will Viṣṇu, then, the Holder of the discus, like to come into this womb! The slayer of Madhu, the Vaiṣṇavas say, entered all at once into the wombs of Kauśalyā and Devakī, full of faeces and other dirty things, of His own free will. But you must think out what happiness can Madhusūdana, quitting his Vaikunṭha Heavens, attain in this womb, full of so many troubles, and where arise, like poisons, hundreds of cares and thoughts to torment an individual! Especially when it is seen that human beings perform asceticism, sacrifice Yajñas and do various charities, that they would avoid thus entering in wombs, which is very painful and terrible. How can Bhagavān Viṣṇu be called independent? If so, He would never have yielded to enter into various wombs. Therefore, O king! Know this that this whole universe is under the control of Yoga Māyā;........."
I hope this clarifies all queries. Prd..