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.
1 min read
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- Period predictions
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- Feeding log
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- Mothers’ community
- Due date calculator
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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
- Ad-free with Premium
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
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
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.
Open calculator
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.
Get the appSmart predictions
Personalized forecasts for your period, fertile days and ovulation — sharper the more you log.
Gentle reminders
Pills, appointments, vaccines, water — quiet nudges exactly when you need them.
Doctor-reviewed library
200+ articles on cycle health, pregnancy and baby — written and checked by clinicians.
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.
“A wonderful app — I used it with my first child too. Alhamdulillah, it is keeping me company with the second one as well. Every week, knowing what changes are happening in me and in the baby I am expecting is very interesting for me.”
Odina A.
“The Lalu — Pregnancy School app is a wonderful school that tells us pregnant women how our little one is developing and gives us mothers the advice we need! My husband and I sit fighting over the phone, waiting for Monday to come round and the weekly advice to change! Big thanks to the people who thought up this app! LALU, we love you.”
Google Play review
“From the very first day of my pregnancy it was with me, and it is still with me now. My baby was born and is nine months old now. And it is with me again, together with me in raising my child too. Thanks be to Allah, it is great, thank you.”
Rozaxanim A.
“I really liked this app, I have been using it since 2023. In this app women talk to each other, ask about the things they do not know and learn them, and it also gives weekly information about what is changing in the mother and in the baby.”
Zuleyha N.
“Lalu — thank you! Every day at first light I open my eyes and look at you (even though everyone else looks at Telegram), as if something could have changed in the space of an hour. Thanks to you my pregnancy is passing calmly, because in Lalu you can find an answer to every question. For about a month now you have become all I think about. I am waiting impatiently for my child to come into the world. Five stars to the creators of the app!”
Google Play review
“A really great app. What I like most is the message from your baby section, I read it in tears every time. Thank you to the app’s creator.”
Malika T.
“Peace be upon you. I downloaded the Lalu — Pregnancy School app onto my phone in the very first days after I found out I was pregnant. I have been with Lalu for 13 weeks and I will stay from now on too, and if you ask why — I have no experience in raising a baby! That being so, I trust Lalu and I get advice from experienced mothers. I recommend to you, and to mothers like me, that you download this app. In it you and your baby will feel at ease.”
Google Play review
“I heard about it from a friend of mine, then I downloaded it, and I really liked it. Lalu is a really useful app, you send news every week. We used to sit at home saying, ‘this is happening, what could it be?’ And now when we open it, a notification comes saying that in this month such and such happens. Whoever thought this up, hats off to them. Well done.”
Aziz S.
“It turns out to be a very good app. Until I gave birth I looked at it every week, I got very good advice. Now, after giving birth, I still check it every month. Thank you to the person who created this app.”
Shaxlo A.
“I really like this app. Right now I am pregnant with my third child, and I have used this app since my very first pregnancy. Short and to the point — super.”
Nazokat M.
“Can’t fault it. Very useful. Especially for those becoming a mother for the first time, it gives good advice and knowledge.”
Umida S.
“I really liked this app. I am getting daily information about my little one and daily useful advice about myself.”
Zarina B.
Why trust Lalu
Care you can rely on
Reviewed by doctors
Every health article is written and checked by OB-GYNs, pediatricians and nutritionists.
Private & secure
End-to-end encryption, no data selling, and full control to export or delete — anytime.
Built on science
Predictions use established cycle science, refined to your own patterns over time.
Doctor-reviewed
Content reviewed by a panel of women’s-health clinicians before it reaches you.
Medically reviewedFrom the journal
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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