recovery after childbirth
Refers specifically to the mother's physical recovery and convalescence following childbirth. Often used in the context of traditional postpartum care.
growth of a child
Describes a child's physical development and thriving, often used in older or traditional contexts. Modern Japanese more commonly uses 成長 or 発育.
Since my recovery after childbirth isn't going well, I decided to rest at my parents' house for a while.
This child's growth is fast; they've already started walking.
Compound of 肥 (hi, 'fattening; nourishment') and 立ち (tachi, 'standing; starting'), literally 'getting fat/healthy'. The exact historical derivation is uncertain, but it likely originated from the idea of regaining strength and flesh after childbirth or during childhood growth.