Final answer:
A regular heartbeat can be detected at around 6 weeks gestation, while the fetus's hearing develops around 18-20 weeks gestation.
Step-by-step explanation:
In fetal development, a regular heartbeat can be detected around 6 weeks gestation, or about 4 weeks after conception. At this stage, the heart is beginning to form and can be heard using a Doppler device or ultrasound. The fetal heart tones become more distinct and easily recognizable as the pregnancy progresses.
Playing music for an unborn baby is a common practice, but the fetus's hearing development starts around 18-20 weeks gestation, or approximately halfway through the pregnancy. At this point, the structures involved in hearing, such as the ears and nerves, have developed enough for the fetus to perceive sound vibrations.
It is important to note that the quality of fetal heart tones and the ability to detect them may vary based on factors such as the mother's body shape, the position of the fetus, and the equipment used for monitoring.