Your fertile window, explained — and how to actually find it
There are only about six days each cycle when pregnancy is possible. Here is the science of timing them — without the guesswork.
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Period tracking, pregnancy week-by-week and baby care — in one place that grows with you. When life changes, your data never starts over.
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Ovulation tomorrow
Your most fertile day
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Week 24
As big as a corn cob
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Vaccine in 9 days
We’ll remind you
- Period predictions
- Fertile window
- Week-by-week pregnancy
- Kick counter
- Contraction timer
- Feeding log
- Sleep tracking
- Growth charts
- Vaccine reminders
- Doctor-reviewed articles
- Mothers’ community
- Due date calculator
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200+doctor-reviewed articles
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How it works
One app for every chapter
Cycle, pregnancy, baby — Lalu shifts with you. Switch modes anytime; everything you’ve logged comes along.
Cycle tracking
Understand your cycle, effortlessly.
Log in seconds and let Lalu learn your rhythm. Clear predictions, gentle insights, and a calendar that finally makes sense.
- Period & PMS predictions
- Fertile window & ovulation
- Symptom & mood tracking
- Private and ad-free, always
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Next period · Mar 22
in 11 days
Pregnancy
Follow every week of pregnancy.
Watch your baby grow week by week, with doctor-reviewed guidance for your body and theirs — and reminders for what matters.
- Week-by-week development
- Kick & contraction counters
- Doctor-reviewed articles
- Appointment reminders
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First kicks soon
Usually weeks 18–22
Baby care
Calmer days with your baby.
Track feeds, sleep and diapers in a tap, follow growth against WHO charts, and never miss a vaccine — even at 3 a.m.
- Feeding, sleep & diaper log
- Growth & WHO percentiles
- Vaccination schedule
- Milestones & gentle tips
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Nap ended · 2h 10m
Logged automatically
Free tools
Answers in seconds, no app needed
Quick calculators for the questions every mother googles — free, private, doctor-informed.
Due date calculator
Find your estimated due date, current week and trimester from your last period or conception day.
Open calculatorOvulation calculator
See your next fertile window, most fertile days and expected ovulation from your cycle dates.
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Weeks to months
Translate pregnancy weeks into months and trimesters — and see exactly where you are.
wk 1wk 24wk 40
hCG calculator
Check how fast your hCG level is rising between two blood tests, with typical ranges by week.
Open calculatorFeatures
Everything you need, beautifully simple
Powerful where it counts, calm everywhere else.
At a glance
See your whole month at once
Period, fertile window and ovulation, mapped onto one clean calendar. Tap any day to log or look ahead — no clutter, no guesswork.
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Smart predictions
Personalized forecasts for your period, fertile days and ovulation — sharper the more you log.
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Gentle reminders
Pills, appointments, vaccines, water — quiet nudges exactly when you need them.
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Doctor-reviewed library
200+ articles on cycle health, pregnancy and baby — written and checked by clinicians.
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Private by design
Your body is your business. Data is encrypted, never sold, and yours to export or delete.
Loved daily
A million women, one quiet companion
Real notes from the Lalu community.
“I went from confused about my cycle to actually planning around it. The predictions are scary accurate.”
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Sofia M.
“The week-by-week pregnancy view made me feel held the whole time. I read it every single morning.”
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Amina R.
“Logging feeds and naps at 3 a.m. with one thumb — this app gets new parents. Lifesaver.”
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Daniela K.
“Switched from three separate apps to just Lalu. Cycle to pregnancy without losing a single entry.”
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Yulia T.
“The due date calculator matched my doctor’s estimate to the day. That won me over instantly.”
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Nargiza S.
“Finally an app that doesn’t feel clinical. It’s warm, it’s calm, and nothing is behind a guilt trip.”
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Elif A.
“My husband gets the vaccine reminders too. We’ve never missed an appointment since.”
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Kamila B.
“The fertile-window forecasts helped us conceive after 8 months of trying. Forever grateful.”
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Marta G.
“Articles are short, kind and actually reviewed by doctors. I trust what I read here.”
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Aisha D.
“Growth charts against WHO curves, right in my pocket. Our pediatrician was impressed.”
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Vera L.
Why trust Lalu
Care you can rely on
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Reviewed by doctors
Every health article is written and checked by OB-GYNs, pediatricians and nutritionists.
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Private & secure
End-to-end encryption, no data selling, and full control to export or delete — anytime.
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Built on science
Predictions use established cycle science, refined to your own patterns over time.
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Doctor-reviewed
Content reviewed by a panel of women’s-health clinicians before it reaches you.
Medically reviewedFrom the journal
All articles Useful reads for every stage
FAQ
Questions, answered
Yes — the core of every mode (cycle, pregnancy and baby tracking) is free to use. Lalu Premium unlocks unlimited predictions, the full article and video library, and detailed reports, with a 3-day free trial.
That’s the whole idea. Switch from cycle to pregnancy to baby care anytime, and everything you’ve logged stays with you — no new app, no fresh start.
Lalu uses established cycle science and adapts to your own patterns. The more you log, the sharper your period, fertile-window and ovulation forecasts become.
They use the same standard methods doctors start from — Naegele’s rule for due dates, cycle-length math for ovulation. They’re reliable estimates, not diagnoses; an early ultrasound and your own doctor always have the final word.
Always. Your data is encrypted and never sold. You can export or permanently delete everything from settings, whenever you like.
Every article is written and reviewed by qualified clinicians — OB-GYNs, pediatricians and nutritionists — and updated as guidance evolves.
Your body, finally understood
Download Lalu and start where you are — your first cycle, your first kick, or your first sleepless night.
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