The question worth asking properly
Are baby heartbeat apps safe
Physically, a microphone app is about as inert as software gets. It emits nothing, because there is nothing to emit. That is the easy half, and it is the half everybody stops at.
Three real recordings, three verdicts, decided in your browser. The third is a refusal.
Firstsong is not a medical device, not a doppler and it does not use ultrasound. It cannot tell you that your baby is well and it cannot detect distress. If you notice fewer movements than usual, call your midwife or maternity unit now. Do not listen first, and do not let a sound from a phone change that.
The physical answer, which is the easy half
A doppler sends ultrasound into your body and measures what bounces back off moving blood. That is why it reaches further and why it makes that galloping sound. Energy goes in by design, because that is how it functions.
A microphone app does the opposite. It sits on your skin and listens to pressure waves already leaving your abdomen. Nothing travels inwards, because a microphone has no way to send anything anywhere. It is closer to a stethoscope with better arithmetic than to a scanner. Whatever else is worth worrying about, exposure is not on the list.
| Home doppler | Microphone app | |
|---|---|---|
| How it works | Sends ultrasound in, listens to the echo | Listens to sound already coming out |
| Energy into your body | Yes, by design | None. There is nothing to send |
| Common failure | A strong reassuring sound that is the placenta or your own vessels | The same, plus a printed number that was never real |
| The risk that matters | False reassurance | False reassurance |
So what is the actual risk
It is that you hear something, you feel better, and you do not make a phone call you were about to make. That is the whole risk of this category in one sentence, and it is serious enough that midwives and charities have campaigned on it for years. It applies to ours too.
It is dangerous because the sound is not connected to the question you are asking. A heart rate is one number at one moment. It cannot rule anything out, and a rhythm in a normal range is entirely compatible with a situation that needs attention today. Meanwhile the thing that does carry information, your baby's pattern of movement, gets pushed aside for something that feels more concrete because it has a number on it.
The rule, and it has no exceptions. If your baby's movements have changed from their usual pattern, that is a call to your midwife or maternity unit right now, whatever you can or cannot hear. The NHS guidance is here and Kicks Count exists because of this. Neither mentions listening devices.
Three ways an app here can do harm
It delays a call
The serious one. You were worried, you listened, you heard a rhythm, and the worry eased enough that you waited until morning. Nothing about that rhythm justified waiting, and no amount of engineering removes this, because the failure is in what the sound makes you feel.
It manufactures panic
The other direction, and far more common. You hear nothing on an ordinary evening and spend two hours convinced something is wrong. Nothing was. Any app that leaves you interpreting its own silence has done this to you.
It becomes a substitute
The slow one. Nightly listening becomes the way you check in, and attention drifts from what your baby is doing to what the phone is showing. That swap is a downgrade, and it is why this app has no streak and no reminder.
None of those three is a software bug. They are consequences of how a sound lands on a worried person, so the only defence is what the app says out loud and what it refuses to build.
See what refusing looks like
The third recording in the tool is real audio with no rhythm that holds. Most things here would print a number over it. Watch this one decline and say why. An app that can say no is the only kind you can trust when it says yes.
Runs in your browser. Nothing uploaded, no account, no cookie.
What Firstsong does about it
Design decisions, not disclaimers. A disclaimer at the foot of a screen does no work at eleven at night.
- It repeats the movements advice where it matters. Not once in onboarding and never again. Every time it finds nothing, and every time it finds something: this says nothing about how your baby is doing, and changed movements means call now.
- It never says everything is fine. No green tick, no all clear, no reassuring colour. It reports what it heard and stops. It does not monitor your baby and it does not pretend to.
- It explains its own silence. Nothing found, this on its own means nothing is wrong, and here is why it might have happened. Unexplained silence is what creates the two hour panic.
- No streaks, no nudges, no notifications. The habit loop is how this becomes a substitute for paying attention, so it is not built.
- It names your own heart out loud. Your own doubled pulse is not just a wrong number, it is false reassurance with a number on it. Explained here.
The small safety point nobody mentions
Amplification. Making a very quiet sound audible means high gain, and everything else reaching the microphone is amplified by the same amount. A knuckle brushing the phone, a cough, the case shifting against fabric. Those arrive in your headphones far louder than the heartbeat you were straining to hear. Start with the volume low and raise it slowly, particularly with in ear headphones. It is the only physical risk in the whole exercise.
Privacy is a safety question too
Audio of your pregnancy is about as personal as recorded data gets, and here it is routinely handled by servers you cannot inspect. Firstsong does the analysis on the device. No audio, no heart rate and no gestational age leaves your phone, recordings you keep live on the device and in your own private iCloud, and there is no account.
This website behaves the same way: no cookies, no analytics, no third party requests, which you can confirm in your browser network tab right now. The privacy page sets out the rest, including the one thing we do store, which is an email address if you give us one.
One email, the day it opens
Firstsong is not on the App Store yet. Leave an address and you get exactly one message when it is, with the price on the first line. No newsletter, no drip, no partner offers. You can reply to that email and a person reads it.
Stored on our own server, never sold, never shared. Your IP is hashed, not kept. Nothing about your pregnancy is asked for or stored.
Common questions
Does the app send anything into my body?
No. It is a microphone and a filter. No transmitter, no ultrasound, no emission of any kind. Your iPhone is doing what it does when you make a voice memo, with different arithmetic applied afterwards.
Is it safer than a home doppler?
In pure physics there is nothing to compare, because one puts energy into you and the other does not. In the way that actually matters they carry the same risk, which is that a reassuring sound stops you making a call you should make. So the physics is better and the danger is identical. Anybody giving you only the first half of that is selling something.
Can it tell me if my baby is in trouble?
No. It cannot diagnose anything, it cannot rule anything out and it cannot detect distress. Fetal wellbeing is assessed with continuous tracing and a clinical picture around it, which is why ACOG describes those tests rather than a single number.
Is it safe to use every day?
There is no physical reason it would not be, since nothing is emitted and nothing accumulates. The reason we would rather you did not is behavioural. Daily listening becomes the way you check in, and it is a much worse instrument than noticing what your baby is doing.
Who is behind this and is anybody medical involved?
There are no clinicians on the team and no page here is reviewed by a doctor. We say so in the footer of every page, because borrowing authority we have not earned is how this category talks. What we show instead is the engine, running in your browser, on data anybody can download.
Keep reading
- Do baby heartbeat apps work. the sceptical question, with the measured detection rates
- Is it my heartbeat or the baby. false reassurance with a plausible number attached
- Home dopplers and what midwives warn about. why more power is not more safety
- Hear the difference. the engine live, including the recording it refuses
Last checked 2026-08-23