Transient Tachypnea of the Newborn (TTN): This condition is common in newborns, especially after a vaginal delivery. The symptoms of labored breathing and tachypnea, along with the absence of other severe signs, make TTN a likely diagnosis. The baby's ability to maintain adequate urine output and the lack of severe hypoxia or hypercapnia also support this diagnosis.

Respiratory Acidosis: The low pH (7.329) and low bicarbonate (HCO3 6) levels, combined with the elevated pCO2 (11.7 is not elevated, but in the context of respiratory distress, it may indicate some degree of respiratory acidosis), suggest that the newborn is experiencing some degree of respiratory acidosis. However, the primary issue seems to be metabolic acidosis given the base excess and HCO3 levels.
Infection (e.g., Pneumonia): Although the baby has adequate urine output, infection should always be considered in a newborn with respiratory distress. The presence of tachypnea and labored breathing could be indicative of an early infection.
Metabolic Acidosis: The significant base deficit (-16) and low bicarbonate level (6) point towards a metabolic acidosis. This could be due to various causes including but not limited to infection, congenital metabolic disorders, or issues related to the newborn's adaptation to extrauterine life.

Congenital Heart Disease: Although the BNP (162) is not significantly elevated, which might suggest against severe cardiac dysfunction, congenital heart disease can present with respiratory distress and should always be considered. Echocardiography would be crucial in diagnosing this condition.
Pneumothorax: This is a life-threatening condition that requires immediate diagnosis and treatment. The presence of labored breathing and tachypnea, especially if worsening or accompanied by signs of distress, should prompt an urgent chest X-ray to rule out pneumothorax.
Sepsis: Neonatal sepsis can present with non-specific signs including respiratory distress. Given the potential for severe outcomes, sepsis should always be considered and evaluated for, even if other signs are not present.

Congenital Diaphragmatic Hernia: Although less likely given the absence of more specific signs like severe respiratory distress immediately after birth or a scaphoid abdomen, it remains a differential diagnosis that could explain respiratory symptoms.
Surfactant Deficiency Disorder: More typical in preterm infants, but can occur in term infants, especially if there's a family history or other predisposing factors. The presentation would typically include severe respiratory distress shortly after birth.
Other Rare Congenital Anomalies: Various other congenital anomalies affecting the respiratory or cardiovascular system could present with similar symptoms, though they are less common and would typically be associated with other specific findings on physical examination or initial imaging studies.