Interpretation of the fetal heart rate (FHR) during labor is a common but complex task that requires a significant amount of knowledge about fetal pathophysiology, the changes that may indicate evolving fetal acidemia, and the interventions that may address the underlying cause of these FHR changes. This collection of manuscripts provides important information necessary to successfully identify the infant at risk of acidemia and the knowledge base to understand how best to prevent this complication.
We present a systematic approach to identify the fetus at risk for evolving acidemia. This process requires the caregiver to identify changes that indicate reduced perfusion of the fetus or decreased delivery of oxygen. With an understanding of the time course of the evolution of acidemia, one can estimate the time to potential injury and determine if early intervention is indicated to prevent hypoxic injury.
The clinical context in which changes occur is necessary for the correct interpretation of FHR changes. Preexisting conditions such as advanced maternal age, diabetes mellitus, hypertension or fetal growth restriction may indicate a chronic state of hypoxia and a diminished reserve of the fetus to acute changes that may occur during labor. The ability of the fetus to tolerate recurrent episodes of decreased oxygen delivery may indicate a need for more prompt intervention. Acute changes that may affect the rate of acidemia development are also discussed in this issue.
In this series, you will find a review of the most common interventions, including an assessment of the evidence of efficacy for each intervention and a step by step plan for management of the category II FHR tracing to help guide interventions. Common scenarios when FHR changes don’t fit neatly into an algorithmic approach are also reviewed.
There are critical times during labor when the risk of fetal hypoxic injury may be highest. These are times of transition, the first hour after admission or last hour before delivery, when a series of complicated steps are required to assess the fetal status, identify potential risk factors and problems and to establish an appropriate plan for ongoing monitoring. In this issue, we provide a checklist for care during these critical times.
I am grateful to the authors for their thoughtful and valuable contributions to this issue.