Maternity Nursing: Antepartum Q 21

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During a prenatal visit at 38 weeks, a nurse assesses the fetal heart rate. The nurse determines that the fetal heart rate is normal if which of the following is noted?

  

     A. 80 BPM

     B. 100 BPM

     C. 150 BPM

     D. 180 BPM

    

    

Correct Answer: C. 150 BPM.

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The fetal heart rate depends on gestational age and ranges from 160-170 BPM in the first trimester but slows with fetal growth to 120-160 BPM near or at term. At or near term, if the fetal heart rate is less than 120 or more than 160 BPM with the uterus at rest, the fetus may be in distress.

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Option A: Data from a recently published study in a different context (Serra et al., 2009) is compatible with the findings of our exploratory analysis with a lower limit of 115 or 120 bpm for the gestational ages. Data for the 97th and 99th percentiles are not shown in this study. But shifting the lower limit to 120 will increase the number of false alarms whereas a lower limit of 115 will inevitably increase the risk to misinterpret maternal heart rates as fetal heart rate.

Option B: A lower limit of 120 bpm leads only near term to more false alarms since normal FHR decreases further, and is more appropriate, to avoid misinterpretation of maternal heartbeat as FHR.

Option D: The upper limit of 160 bpm raised concerns in the FIGO meeting in 1985, as Saling described abnormal findings in 24% of scalp blood analyses if the baseline was higher than 160 bpm. It could be shown that the current FIGO guidelines based on computerized analyses of the CTG show a high sensitivity to detect fetal acidosis in case of a suspect or pathological classification of the baseline level.

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