Non-Invasive Techniques for Monitoring Fetal Hypoxemia and Acidosis

• Historically, direct percutaneous needle sampling of fetal cord blood provided insights into fetal hypoxemia and acidosis but has largely been replaced by non-invasive techniques.
• Chronic fetal hypoxemia can lead to severe consequences, including fetal demise, intrapartum metabolic acidosis, and long-term neurodevelopmental impairment.
• Significant fetal acidemia is strongly associated with increased perinatal mortality, morbidity, and neurological adverse outcomes.

Integrated Non-Invasive Testing Panel

• Current monitoring strategies integrate ultrasound, fetal heart rate (FHR), and Doppler ultrasound into scores such as the biophysical profile score (BPS).
• The fetus typically tolerates moderate chronic hypoxemia but risks catastrophic outcomes when hypoxemia progresses to metabolic acidosis.

Fetal Heart Rate Analysis

• FHR reflects the brainstem and hypothalamic autonomic control sensitive to hypoxemia.
• Non-Stress Test (NST):
  • Evaluates baseline heart rate, accelerations, and decelerations linked to fetal movements.
  • A normal NST includes at least two accelerations within 20 minutes.
  • A non-reactive NST indicates potential hypoxemia but lacks specificity.
  • Loss of FHR variability in animal studies correlates with increasing acidemia.