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Introduction ⬇

Fetal Oxygen Saturation (SpO2) Monitoring

Fetal oxygen saturation (SpO2) monitoring is used with EFM as an additional means of assessment when the FHR is not reassuring or not interpretable. The fetal SpO2 monitoring system involves a single-use sterile disposable sensor that is inserted through the cervix into the uterus and rests against the fetal temple, cheek, or forehead. The sensor is a reflectance sensor in which a light source and a photodetector are placed next to each other. Backscatter of light (light absorption by pulsing arterial blood) is measured from a vascular bed under the sensor, and when it is reflected back to photodetector, reflected light is analyzed and displayed on the monitor and on the FHR paper tracing. Fetal SpO2 monitoring should only be used after maternal membranes have ruptured and on a singleton fetus in vertex presentation with a gestational age of ≥36 
weeks.

Procedure ⬆ ⬇

  1. Be aware that fetal SpO2 is indicated if there is a nonreassuring FHR pattern.

  2. Perform Leopold maneuvers to determine fetal position and sterile vaginal examination to assess dilation, station, and presentation.

  3. Apply sensors when membranes are ruptured and cervical dilation of ≥2 cm has been achieved with the fetus at station of −2 or below and vertex presentation.

  4. Insert a single-use sterile sensor (proficiency in fetal scalp electrode insertion or intrauterine pressure catheter insertion is necessary). Insert the sensor perpendicularly to sagittal suture. Insertion should be done between uterine contractions.

  5. Attach the sensor to the fetal SpO2 monitor. This monitor may be able to interface with a FHR monitor and record as a continuous line with uterine activity.

  6. Document fetal SpO2 on labor flow sheet as a range (e.g., 40%–45%), and follow standard documentation intervals of other fetal assessments such as FHR.

Clinical Implications ⬆ ⬇

  1. Single measurements of fetal SpO2 are not useful; need to track trends.

  2. Continued fetal SpO2 readings of <30% for >10 minutes are likely to lead to progressive fetal hypoxemia, acidemia, and deterioration in fetal well-being.

  3. Fetal SpO2 monitoring, along with the use of other fetal monitoring, provides the ability to detect a compromised fetus and a healthy fetus with nonreassuring FHR.

  4. Provides data that a fetus with a nonreassuring FHR pattern can safely continue in labor and reduce unnecessary interventions during labor and birth, therefore improving maternal-fetal outcomes and decreasing costs.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain the reason for monitoring and the procedure involved.

  2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Clinical Alert

Contraindications include the following:

  1. Documented or suspected placenta previa

  2. Ominous FHR pattern requiring immediate intervention

  3. Need for immediate delivery not related to FHR pattern

  4. Active genital herpes, hepatitis B or E, or other infections that preclude internal monitoring

  5. Seropositivity for HIV

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed.

  2. Counsel the patient and monitor appropriately during labor. Treat accordingly.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆ ⬇

  1. Vernix can cause interruption in fetal SpO2 monitoring if present in significant quantity. Meconium does not interfere.

  2. Strong uterine contractions may cause temporary loss of the signal from sensor at peak of uterine contractions.

  3. Fetal and maternal movement can displace sensor.

Reference Values ⬆

Normal

Normal range for fetal SpO2 is 30%–70%. Fetal SpO2 of ≥30% between uterine contractions with a nonreassuring FHR indicates the fetus is adequately oxygenated.