The Compendium of Caraka 4.4.27

4.4.27

mātrādīnāṃ khalu garbhakarāṇāṃ bhāvānāṃ saṃpadastathā vṛttasya sauṣṭhavānmātṛtaścaivopasnehopasvedābhyāṃ kālapariṇāmāt svabhāvasaṃsiddheśca kukṣau vṛddhiṃ prāpnoti//

Indeed, from the excellence of the procreative factors such as the maternal one, from the correctness of regimen, from the unction and warmth derived from the mother, from the transformation of time, and from the accomplishment of inherent nature, it attains growth in the womb.