Final answer:
The 3 major changes that normally occur immediately after birth include the baby taking its first breath, the cutting and sealing of the umbilical cord, and the onset of nonshivering thermogenesis for temperature regulation along with the start of gastrointestinal function.
Step-by-step explanation:
The question of what are the 3 major changes that normally occur immediately after birth pertains to key physiological adjustments a newborn undergoes as it transitions from the intrauterine environment to the outside world. These changes are critical for the newborn's survival outside the mother's womb.
Respiratory Adjustments
The first breath a newborn takes at birth is essential for inflating the lungs. This action causes a significant alteration in the circulatory system, closing fetal shunts that previously bypassed the lungs and transitioning the newborn to pulmonary respiration.
Circulatory Adjustments
With the clamping and cutting of the umbilical cord, the three umbilical vessels collapse. The proximal umbilical arteries integrate into the circulatory system, while the distal arteries and the vein become fibrotic, ceasing their previous function of transporting blood between the fetus and the placenta.
Thermoregulation and Gastrointestinal Changes
The newborn begins to maintain body temperature through nonshivering thermogenesis by metabolizing brown adipose tissue. Additionally, the first consumption of milk introduces beneficial bacteria into the newborn's previously sterile gastrointestinal tract, establishing a gut flora for digestion.