Final answer:
The fetal heart rate can typically be first detected using a fetoscope at around 10 weeks gestation, although this may vary depending on certain conditions.
Step-by-step explanation:
The fetal heart rate (FHR) can be auscultated with a fetoscope at different stages of gestation. A fetoscope is a type of stethoscope used specifically in obstetrics for listening to the fetal heartbeat. According to developmental milestones, the regular heartbeat of a fetus can be detected earliest at around 10 weeks of gestation. However, it is important to note that various factors can influence the ability to hear the fetal heartbeat, such as the position of the fetus, the mother's body habitus, and the skill of the healthcare provider.
During the fetal stage, which begins at the end of the 8th week of gestation and continues until birth, numerous developments occur. Starting at around 9 to 15 weeks, all major organs are present though not yet fully functional. By approximately 10 weeks, the heartbeat can generally be detected using a Doppler device. It is around this time that using a fetoscope could also possibly detect the heartbeat, but it might still be difficult, and using ultrasound technology is more common and reliable at this stage.
Thus, the fetal heartbeat is likely to be auscultated with a fetoscope earliest at around 10 weeks gestation, but optimal detection is commonly accomplished with ultrasound.