Question
How was lord Krishna born?
Answer
According to Vishnu Purana, Book 4, Chapter 15, Lord Krishna birth was normal. He has taken birth from the womb of Devaki.
Next, the divine Vishńu himself, the root of the vast universal tree, inscrutable by the understandings of all gods, demons, sages, and men, past, present, or to come, adored by Brahmá and all the deities, he who is without beginning, middle, or end, being moved to relieve the earth of her load, descended into the womb of Devakí, and was born as her son Vásudeva.
According to Shrimada Bhagavatam also Lord Krishna birth was normal. Shrimada Bhagavatam, Canto 10, Chapter 2, Devaki kept him in herself.
SB 10.2.18 — Thereafter, accompanied by plenary expansions, the fully opulent Supreme Personality of Godhead, who is all-auspicious for the entire universe, was transferred from the mind of Vasudeva to the mind of Devakī. Devakī, having thus been initiated by Vasudeva, became beautiful by carrying Lord Kṛṣṇa, the original consciousness for everyone, the cause of all causes, within the core of her heart, just as the east becomes beautiful by carrying the rising moon.
SB 10.2.19 — Devakī then kept within herself the Supreme Personality of Godhead, the cause of all causes, the foundation of the entire cosmos, but because she was under arrest in the house of Kaṁsa, she was like the flames of a fire covered by the walls of a pot, or like a person who has knowledge but cannot distribute it to the world for the benefit of human society.
And then, in Shrimada Bhagavatam, Canto 10, Chapter 3, it is explicitly mentioned that Lord Krishna has taken birth from womb.
SB 10.3.31 — At the time of devastation, the entire cosmos, containing all created moving and nonmoving entities, enters Your transcendental body and is held there without difficulty. But now this transcendental form has taken birth from my womb. People will not be able to believe this, and I shall become an object of ridicule.
Harivamsa Purana, Vishnu Parva, Chapter 4 also confirm that Lord Krishna birth was normal.
After her (seventh) conception was aborted, devakI conceived (for the eighth time), for which, kaMsa had destroyed her seven conceptions. 2.4.8
The ministers (of kaMsa) guarded that conception with careful efforts. But then, hari (viShNu) was residing in her womb at his self will. 2.4.9
The same day, yashodA, conceived nidrA who carries out the instructions of viShNu and who manifested from viShNu's body. 2.4.10
Before the completion of the normal period of pregnancy, the women, devakI and yashodA delivered in the eighth month at the same time. 2.4.11
A girl was born to yashodA at the same time of the same night when kR^iShNa, who elevates the (fame of) vR^iShNi race was born. 2.4.12
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