Fetal Heart Rate Decelerations Precede a Decrease in Fetal Oxygen Content

Abstract

To determine the relationship between abnormal fetal heart rate (FHR) patterns, fetal oxygen content by reflectance pulse oximetry, and the effects of maternal oxygen administration, 158 intrapartum women consisting of 120 women with normal FHR patterns, and 38 women with varying degrees of variable FHR decelerations were examined. A new reflectance pulse oximetry probe was attached to the fetal forehead to continuously monitor fetal oxygen saturation (SpO₂) during labor. Oxygen was administered for 30 min at 5 liters/min by nasal canula in 32 women. No significant change in fetal SpO₂ was seen in women with normal FHR patterns, but a significant decline in SpO₂ was observed shortly before births. FHR decelerations less than 90 bpm occurred prior to the decline in fetal SpO₂ Maternal oxygen administration was effective in increasing fetal SpO₂ in fetuses with decreased SpO₂ (SpO₂ < 50%), but not in fetuses with high SpO₂ (SpO₂ > 60%). It is concluded that fetal SpO₂ exhibits no change during normal labor but significantly declines shortly before birth, that relatively severe variable decelerations (< 90 bpm) can decrease fetal SpO₂, and that maternal oxygen treatment at 5 liters/min is effective in augmenting fetal oxygen tension in fetuses with decreased oxygen tension.

Fetal heart rate monitoring during fetoscopic repair of open spinal neural tube defects: a single-centre observational cohort study

“…According to the literature, a drop in FHR may precede hypoxia. 18 Thus, monitoring FHR allows early detection and a prompt response. Other fetal monitoring techniques include pulse oximetry, echocardiography, umbilical artery Doppler, and ductus venosus Doppler.…”

Anesthesia for In Utero Repair of Myelomeningocele

“…Fetal arterial oxygen saturation ranges from 40-70% 68 , and bradycardia often precedes oxygen desaturation during human fetal surgery. 69 Umbilical cord arterial flow is periodically assessed to further evaluate fetal well-being and the effects of the anesthetic and surgical procedure on both placental and fetal blood flow. Constant vigilance for maternal and fetal bleeding is needed.…”

Anesthesia for In Utero Repair of Myelomeningocele

“…Fetal arterial oxygen saturation ranges from 40–70% 68 , and bradycardia often precedes oxygen desaturation during human fetal surgery. 69 Umbilical cord arterial flow is periodically assessed to further evaluate fetal well-being and the effects of the anesthetic and surgical procedure on both placental and fetal blood flow. Constant vigilance for maternal and fetal bleeding is needed.…”