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Six pieces, none of them padded, all written so that somebody who never buys anything still leaves knowing something true.
The engine, running on three real recordings, in your browser.
None of this is medical advice and Firstsong is not a medical device. If you notice fewer movements than usual, call your midwife or maternity unit now. That call is always the right one to make.
The short answers live in Answers. These are the ones where a paragraph was not enough, either because the physics needed explaining or because the honest answer needed room to not sound like a brush off.
- Anterior placenta, and why your belly sounds further away than everyone else's. The front wall is an ordinary place for a placenta to sit. It is also directly between your baby and the microphone. What that does to sound, and what to do.
- Home dopplers, what midwives actually warn about. The warning is not really about the ultrasound. It is about what a reassuring sound does to the phone call you were about to make. And what an app is not.
- Is that my heartbeat, or the baby's. A resting pulse doubled is the failure mode of this whole category. The physics of it, a check you can run with your own hand, and what an honest engine does.
- The arm test, and what it tells you in thirty seconds. Put the phone on your forearm, then on a cushion. An honest app gives an adult rate on one and nothing on the other. Run it on every app in this category.
- What a phone can and cannot pick up, week by week. Detection rates we measured band by band across the third trimester, why the middle dip is not real, and the honest reason nothing is promised any earlier.
- You cannot hear anything, and it is the middle of the night. A phone that finds nothing has told you about the room, the angle and the week. It has not told you about your baby. What blocks the sound, and what does matter.
The fastest way to see the point
Every piece here comes back to the same thing: an engine that can say no. You can watch one do it on three real recordings without installing anything.
Runs in your browser. Nothing is uploaded.
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.
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Last checked 2026-08-23