The most common cause of decreased variability in the FHR that lasts 20 minutes or less is:

Choice A rationale
Limited perception of bladder fullness can occur with epidural anesthesia, but it is not the most common or harmful complication. Patients should be monitored for urinary retention.
Choice B rationale
Severe afterbirth headache, or post-dural puncture headache, can result from epidural complications, but it is less common than hypotension.
Choice C rationale
Hypotension is the most common and potentially harmful complication of epidural anesthesia. It occurs due to sympathetic nerve blockade, leading to vasodilation and decreased cardiac output. Normal blood pressure ranges: systolic 90-120 mmHg, diastolic 60-80 mmHg.
Choice D rationale
Increased respiratory rate is not a common complication of epidural anesthesia. It is more likely related to anxiety or other factors and should be monitored accordingly.

Choice A rationale
The tocodynamometer detects both the frequency and intensity of uterine contractions by measuring the pressure changes on the abdomen. It provides real-time data on contraction patterns during labor.
Choice B rationale
Repeating the frequency and intensity of contractions is redundant. The tocodynamometer accurately measures these parameters, providing essential information for managing labor progress.
Choice C rationale
While the tocodynamometer can infer uterine resting tone, it is not designed to measure hypertonus directly. Other methods, like intrauterine pressure catheters, offer more accurate assessments of uterine tone.
Choice D rationale
The tocodynamometer measures the duration of contractions, but it does not solely focus on this parameter. It captures comprehensive data, including frequency and intensity, for effective labor management.