While the 22-day mark is recognized as the earliest period when a fetus’ heart starts to beat, you won’t be able to tune your baby’s heartbeat this early using an at-home heart rate monitor.
So, when can you hear a baby’s heartbeat with fetal doppler devices? The majority of Fetal Dopplers work best when used in your second or third trimesters, when your baby’s heartbeat is strong enough to register.
That said, there is a pattern to baby heartbeat formation, and, correlatively, how early fetal heartbeat can be detected with clinical or at-home Dopplers:
Week 5 – A little after a month, your baby’s heart emerges as a cohesive beating structure. However, fetal Dopplers will not pick up this sound because they are used transabdominally (by being placed against the mother’s abdomen). Only vaginal ultrasounds can detect a heartbeat this faint at this stage.
Weeks 6 to 8 – During this period, your baby’s heartbeat will rise from 110 bpm (beats per minute) to 150 to 170 bpm—about twice as fast as yours. At this stage, your baby’s heartbeat may be detectable by a clinical Fetal Doppler.
Week 10 – By now, most babies’ hearts beat at 170 bpm. Between now and week 20, it will slow to around 140 bpm. While some at-home Fetal Dopplers pledge to detect your baby’s heartbeat at this stage, most high-quality devices won’t work properly until at least week 16 of your pregnancy. When in doubt, consult with your OBGYN before purchasing and using your device.
Week 12 – By week 12, your OBGYN should have booked or completed your first trimester check-in to verify your baby’s heart is beating. Why? Because research shows that if a baby’s heartbeat is detected past week 10, it has a 99.4% chance of avoiding miscarriage.