Final answer:
Early decelerations in FHR during labor are caused by contractions that reduce oxygenated blood flow to the fetus, leading to fetal distress if not followed by adequate relaxation periods, possibly requiring emergency birth intervention.
Step-by-step explanation:
Early decelerations in fetal heart rate (FHR) can result from the uterine contractions during labor which momentarily decrease the oxygenated blood flow to the fetus. It is necessary that a period of relaxation follows each contraction so that the blood supply and oxygen can be restored. Without this recovery time, fetal distress may occur which is indicated by a sustained decrease in the fetal heart rate. If contractions are overly powerful or too long, and the oxygenation is not adequately restored, this could lead to a need for emergency birth interventions such as vacuum, forceps, or a Caesarian section.