Now the part the app listings do not explain: what your phone is actually picking up when it plays a rhythm back to you. It is worth two minutes of your time, because it changes how you read the result — and because there is one method that tells you far more about your baby’s wellbeing than any sound ever will.
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How the phone apps work
Most of these apps use the phone’s camera or microphone to detect small changes in colour or movement at the skin, and convert those signals into an audible rhythm. It is the same technique used by apps that measure your pulse from a fingertip, and it works well for exactly that.
What it cannot do is reach through the abdominal wall, the amniotic fluid and the placenta. Those layers are what a medical doppler is built to penetrate, using ultrasound — which a phone does not have.
This is where the count from the previous page earns its keep. A baby’s heart runs at 110–160 bpm; an adult resting pulse is 60–100. Count what the app gives you for fifteen seconds and multiply by four. If it lands near your own resting rate, the app is playing your pulse back to you — which is the most common outcome by far.
So are they useless?
Not exactly — but be clear about what you are buying. As a keepsake, a bit of fun, or a way to feel connected between appointments, they are harmless. Several also bundle genuinely useful things: kick counters, contraction timers, week-by-week guides and appointment reminders.
- Do not use one to decide whether the baby is fine. That is the single line that matters on this page.
- Hearing nothing means nothing. Position, placenta and phone quality all produce silence in a completely healthy pregnancy.
- Hearing something means nothing either, unless you have counted the rate and it is in the baby’s range.
What actually tells you your baby is well
Not sound — movement. This is the measure midwives and obstetricians rely on between appointments, and it is the one thing every health service asks expectant mothers to pay attention to:
- Learn your baby’s pattern — there is no universal number of kicks; what matters is what is normal for yours
- Movements should not reduce as you approach the due date. The idea that babies “run out of room” and slow down is a myth
- Check at the times your baby is usually active, often in the evening or after you eat
- Any change in the pattern is worth a phone call — not a wait-and-see
If movements change
Call your midwife or maternity unit. Straight away.
Day or night, every day of the week. Never wait until morning, never wait for the next appointment, and never use a phone app or a home doppler to decide whether the call is necessary. They would always rather check.
Frequently asked questions
Is there any app that genuinely detects a fetal heartbeat?
Some work with an external sensor that plugs into the phone — that is a device doing the work, not the phone. An app using only the camera or microphone is reading signals at the surface of your skin.
Are home dopplers better?
They are real ultrasound devices, but health services and stillbirth charities advise against relying on them at home for the same reason described above: a reassuring sound can delay a call that should have been made.
Is it harmful to use one?
The app itself does nothing to you or the baby. The risk is entirely in what you decide based on it.
What is the safest way to feel connected between appointments?
An ear on the belly from around 20 weeks, and paying attention to movement patterns. Both are free, both are passive, and one of them is genuinely informative.
Notice: this is an independent informational content portal. We have no affiliation with the apps, devices or organisations mentioned. The information here is educational and does not replace antenatal care, examinations or professional medical advice. If you have any concern about your baby’s movements or wellbeing, contact your midwife or maternity unit immediately — at any hour.