Gynecology & Reproductive Medicine


Novel Hypoxia Index in Fetal Heart Rate Monitoring

Kazuo Maeda, MD, PhD

Aims: Creation of novel objective & numeric fetal hypoxia index, solving controversy pattern classification, preventing cerebral palsy caused by intrapatum fetal brain damage before definite threshold.

Methods and Results: Hypoxia index (HI) is the sum of deceleration duration (min) divided by the lowest FHR (bpm), and multiplied by 100. As the HI was 25 in a case of abnormal FHR followed by the cerebral palsy (CP), and 26 in a case of repeated late decelerations (LD) for 50 min with the loss of variability, Apgar 3, and brain damage, while abnormal FHR whose HI was 20-24 developed neither loss of variability nor CP. The HI was 6, Apgar score was 9 and no CP in a case of 3 connected LDs. Apgar score was predicted by a regression equation.

Discussion: LD is ominous because of its high repetition producing high HI, while 2-3 LD repetition develops no ominous outcome. The principle can be adapted to the other decelerations and sudden continuous fetal bradycarda. Computerized FHR diagnosis is simplified introducing hypoxia index, rejecting subjective pattern classification and early delivery before reaching 25 of HI will prevent the brain damage and CP.

Conclusion: The late, early and variable decelerations and sudden FHR bradycardia will be followed by neither fetal brain damage nor CP, if the HI was lower than 25 during delivery, while normal neonate without CP will not be expected if fetal HI was 25 or more, despite fetal death was prevented. HI is the most effectively applied in computerized FHR monitoring, at the same time with the FHR score, FHR curve frequency spectrum and A/B ratio.