Final answer:
The postnatal period, also known as the postpartum period, is approximately six weeks long and starts after the placenta is delivered. It involves significant physiological changes for both mother and newborn as they adjust to life outside the womb.
Step-by-step explanation:
The postnatal period is traditionally defined as the time frame after birth during which the mother's body returns to a non-pregnant state. This period begins immediately following the delivery of the placenta, and it is a critical transition time for both the mother and the infant. In this context, the postnatal period specifically refers to the postpartum period, which is approximately six weeks long.
During the postpartum period, the mother experiences various adjustments, including uterine contractions to reduce blood loss and postpartum vaginal discharge called lochia. The newborn also makes significant adjustments post-birth, transitioning from fetal life where everything is provided by the placenta to independently regulating body temperature, breathing air, and processing nutrition. The term 'neonatal period' refers to the first 30 days of life outside the uterus for an infant, where they adapt to the environmental changes and experience hunger and thirst for the first time.