If your menstrual cycle is typically 34 days long and your last period started on March 25th, 2022, you can expect to hear your baby's heartbeat around the sixth or seventh week of pregnancy. This usually occurs between the fifth and eighth week after the start of your last period. However, it's important to note that individual variations exist, so it's best to consult with your healthcare provider for a more accurate estimation based on your specific circumstances. They may recommend an ultrasound or Doppler examination to detect and monitor the fetal heartbeat.