01
Microscope
Apply a tiny saliva sample to the lens and let it dry. Saliva crystallises as you enter your fertile window.
Saliva fertility test · CE marked
Find out when you are most likely to get pregnant.
Babyndex pairs a reusable pocket microscope with a mobile app that reads the fern-like crystal patterns in your saliva — so you know your fertile window, not just the day of ovulation.
The app is under development and is intended for informational purposes only, not as a medical device.
Conception probabilityPregnancy probability
Two days before ovulation, not the day of.
Pregnancy is 3–5× more likely when intercourse happens 2 days before ovulation than on the day itself. Most tests tell you ovulation is happening — by then, the most fertile window is already closing.
Saliva starts to crystallise as estrogen rises in the days leading up to ovulation. Babyndex catches that signal early.
Saliva vs. LH tests
Why this matters
Most ovulation tests tell you “you are fertile now”. But conception and clinical pregnancy are not the same thing.
Research shows the chance of conception is similar across the last three fertile days. However, conception two days before ovulation is 3–5× more likely to lead to a clinical pregnancy than conception on the day of ovulation.
up to 5 days
Sperm can stay alive in the reproductive tract
12–24 hours
The egg lives after ovulation
So the best chance is when the sperm are already waiting for the egg.
What the LH urine test shows
It detects the LH surge, which starts about 24–36 hours before ovulation. But LH only becomes detectable in urine later — typically 6–12 hours after it begins. So a positive test often lands in the later part of the fertile window, when the best days (especially day −2) are already partly or fully behind you.
What saliva ferning shows
Saliva crystallises as estrogen rises — and that rise starts earlier than the LH surge. So the microscope can show the beginning of your fertile window, not just its end.
In short
−3, −2
Best chance of clinical pregnancy
- What the LH test shows
- Still negative
- What saliva shows
- Crystals may appear
−1
High chance of conception
- What the LH test shows
- May be positive
- What saliva shows
- Crystals usually visible
0 · ovulation
Conception possible, but lower chance of clinical pregnancy
- What the LH test shows
- Positive
- What saliva shows
- Crystals still visible
The goal is not to hit one exact day — it is to be active at the start and middle of your fertile window, not only once the LH test turns positive.
What is Babyndex?
Three small things, working together every morning.
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Application
Hold the microscope against your phone camera and take a photo. The app recognises the crystal patterns.
03
Calendar
Our algorithm scores the patterns and shows the days with the highest chance of getting pregnant.
Why Babyndex is different.
Actual
Saliva crystallises on your real fertile days — works even with irregular cycles, no months of temperature data required.
Accurate
A 2018 Harvard Medical School study found automated saliva crystal detection predicts ovulation with over 99% accuracy.
Affordable
The microscope is reusable — use it as many times as you want. More sustainable than single-use hormone strips.
From the blog
Our most-read posts on ovulation and the fertile window.
When is my ovulation day?
Cycle length varies, and so does ovulation. Learn how to pinpoint your ovulation day.
When is a woman the most fertile?
The fertile window is short — and the days before ovulation matter most.
Home ovulation tests: regular vs irregular cycles
How LH strips, basal body temperature, and saliva tests compare — and which works best for regular vs irregular cycles.
How to use Babyndex for ovulation prediction
A short walkthrough of the daily saliva test and how the app reads the pattern.
Interpreting the saliva fern test
What dots, lines, and full ferns mean — and how the app removes the guesswork.
Is Babyndex right for you?
A quick check before you start.
Hormonal contraception
The test relies on pre-ovulatory estrogen. Hormonal contraceptives suppress that signal, so it only works if you are not using them.
PCOS
With PCOS, saliva patterns may look different, but the test can still show your actual fertile days. Try it for a full cycle.
Irregular cycles
Unlike LH strips or temperature tracking, saliva crystals show the real fertile window as it happens — no perfect cycle needed.
Try the saliva fern test for one full cycle.
If it doesn't work for you, send the microscope back and we'll refund its price.