Final answer:
If a resuscitated apneic newborn's heart rate increases to 120 bpm, SpO₂ reaches 90%, and begins spontaneous breathing, positive pressure ventilation should be discontinued and the baby monitored.
Step-by-step explanation:
When resuscitating an apneic newborn, if the baby's heart rate (HR) increases rapidly after the first few breaths, is now 120 bpm, oxygen saturation (SpO₂) is 90%, and the baby is beginning to breathe spontaneously, the correct action would be to discontinue positive pressure ventilation and monitor the baby. This response is consistent with neonatal resuscitation guidelines, which suggest that once the newborn achieves adequate spontaneous respirations, a normal heart rate, and satisfactory oxygenation, positive pressure ventilation can be stopped. It is important to continue monitoring to ensure the newborn maintains these normal parameters and does not require further intervention.