What is the first intervention when late decelerations are observed in fetal heart rate tracing?

When late decelerations are observed in fetal heart rate tracing, the primary concern is fetal well-being, as these decelerations can indicate compromised oxygenation to the fetus. Positioning the mother to her side is the first recommended intervention because it can help improve uteroplacental blood flow, thereby reducing the risk of fetal distress. Side-lying positions, particularly the left side, are known to optimize venous return and may help alleviate any potential compression on the umbilical cord.

Ensuring adequate oxygenation for the mother is also critical, as improved maternal oxygenation can enhance fetal oxygen delivery. This intervention is both non-invasive and prompt, facilitating immediate adjustments to improve the fetal condition without delay.

Other options involve medical interventions that may be necessary later, such as administering medication or increasing fluid intake, but they do not address the immediate need for modification in maternal position and oxygenation. Surgical interventions like a C-section are typically reserved for more severe situations and would not be the first response to late decelerations unless there is a clear indication of emergent fetal distress. Hence, the best initial response prioritizes maternal-fetal repositioning and oxygenation, thereby making it the correct choice.