Asphyxia at birth, also known as birth asphyxia or neonatal asphyxia, is a condition where a newborn infant experiences a lack of oxygen (hypoxia) and/or inadequate blood flow (ischemia) before, during, or immediately after delivery. Diagnosing asphyxia at birth is a complex process that involves clinical assessment, laboratory tests, and sometimes imaging and neurological monitoring to determine the severity and guide treatment.
The diagnosis begins immediately after birth with a thorough clinical evaluation of the newborn’s condition. One of the most widely used tools is the **Apgar score**, which assesses five vital signs at 1 and 5 minutes after birth: heart rate, respiratory effort, muscle tone, reflex irritability, and skin color. Each sign is scored from 0 to 2, with a maximum total of 10. A low Apgar score (especially below 5 at 5 minutes) suggests possible asphyxia but is not definitive on its own because other factors can influence the score.
Beyond the Apgar score, clinicians look for signs of **respiratory distress**, such as irregular or absent breathing, cyanosis (bluish skin), and poor muscle tone. The infant may also show signs of **cardiovascular compromise**, including a slow or irregular heart rate. These clinical signs raise suspicion of asphyxia and prompt further evaluation.
Laboratory tests play a crucial role in confirming the diagnosis and assessing the severity of oxygen deprivation. One key test is the measurement of **umbilical cord blood gases** immediately after birth. This involves analyzing the pH, partial pressure of oxygen (pO2), and carbon dioxide (pCO2), as well as lactate levels. A low pH (acidosis) and elevated lactate indicate that the baby experienced significant oxygen deprivation. Typically, a cord blood pH below 7.0 and a base deficit greater than 12 mmol/L are considered markers of severe asphyxia.
In addition to blood gases, other blood tests may be performed to evaluate organ function affected by hypoxia. For example, elevated levels of enzymes such as **aspartate aminotransferase (AST)** and **alanine aminotransferase (ALT)** can indicate liver injury, while increased **creatinine** and **blood urea nitrogen (BUN)** suggest kidney impairment. Elevated **troponin** levels may reflect cardiac stress or injury due to hypoxia.
Neurological assessment is essential because asphyxia can cause hypoxic-ischemic encephalopathy (HIE), a brain injury resulting from oxygen deprivation. Clinicians observe the infant’s level of consciousness, muscle tone, reflexes, and seizures. To support clinical findings, **electroencephalography (EEG)** or amplitude-integrated EEG (aEEG) may be used to monitor brain activity and detect abnormalities consistent with HIE. These tools help in grading the severity of encephalopathy and guiding treatment decisions.
Advanced monitoring techniques, such as **near-infrared spectroscopy (NIRS)**, can non-invasively measure cerebral oxygenation and blood flow in real time. This helps in assessing neurovascular coupling and autoregulation in the brain, providing early warning signs of worsening brain injury.
Imaging studies, particularly **cranial ultrasound** and **magnetic resonance imaging (MRI)**, are often performed within the first days or weeks after birth to visualize brain injury patterns typical of asphyxia. MRI is especially valuable for detailed assessment of brain structures and predicting long-term outcomes.
In some cases, additional cardiac evaluations like **echocardiography** and **electrocardiogram (ECG)** are conducted to assess heart function and detect complications such as ventricular hypertrophy or ischemic injury, which may accompany severe asphyxia.
The diagnosis of birth asphyxia is therefore a multi-step process combining immediate clinical assessment