When can the baby's fetal heart sound (FHS) be heard by stethoscope?

Appeared in: Bihar CHO -2019

Explanation

Fetal heart sounds (FHS) become audible with a standard acoustic or Pinard stethoscope around 18 to 20 weeks of gestation.
Among the given choices, 20 weeks is the most accurate milestone for when FHS can be reliably detected using a stethoscope.
This is distinct from detection with a handheld Doppler, which can pick up the heartbeat much earlier, typically between 10 and 12 weeks.
The normal fetal heart rate (FHR) ranges from 110 to 160 beats per minute.

Option A: This is incorrect. While FHS is clearly audible at 24 weeks, it can be detected much earlier with a stethoscope. This option represents a point well after the initial detection window.
Option B: This is incorrect. Similar to 24 weeks, FHS is easily heard at 28 weeks, but this is not the earliest time it can be detected with a stethoscope.
Option D: This is incorrect. At 14 weeks of gestation, the fetal heart is too small and the sound is too faint to be picked up by a conventional or Pinard stethoscope.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Auscultation of Fetal Heart Sounds (FHS) during pregnancy as background academic context rather than a clinical decision trigger.
Auscultating FHS is a fundamental nursing skill in antenatal care to confirm fetal viability and assess well-being.
It is crucial for the nurse to differentiate the FHR from the maternal pulse by simultaneously palpating the mother's radial pulse while listening. If the rates are the same, the nurse is likely hearing the maternal aorta.
The location for best hearing the FHS changes with fetal position and gestational age. After 20 weeks, it's typically heard below the umbilicus for a cephalic presentation and above for a breech presentation.

How to Approach the Question

First, identify the key components of the question: 'fetal heart sound (FHS)' and the instrument 'stethoscope'.
Recall that there are different methods for detecting FHS, primarily the stethoscope (or fetoscope) and the electronic Doppler.
Differentiate between the sensitivity of these tools. A stethoscope is an acoustic device and is less sensitive than an electronic Doppler.
Remember the standard clinical timeline: Doppler detects FHS around 10-12 weeks, while a stethoscope can detect it around 18-20 weeks.
Compare this timeline to the options provided.
Select the option that aligns with the 18-20 week timeframe for a stethoscope, which is '20 Weeks'.

Concept Tested & Keywords

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E6 Comprehensive Textbook of Community Health Nursing for BSc Nursing Students Part 2 — Subpart A (pp 1-275 of 550) p. 200-202

E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart A (pp 1-232 of 464) p. 19-21

Practise the full Bihar CHO -2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.