The Wonder Weeks
The Wonder Weeks generates a personalised developmental calendar based on a baby’s due date, predicting when each of the 10 mental leaps will occur and notifying parents in advance so they understand their baby’s fussy periods, new skills, and how to support each leap.
The app that turns your baby’s worst weeks into something you can understand, anticipate, and actually survive.
The Wonder Weeks is a baby development app based on decades of research by Dutch scientists Dr. Hetty van de Rijt and Dr. Frans Plooij, originally published as the bestselling book “Oei ik groei!” (Oh, I’m Changing!). The core insight behind the app and the research it is built on is that all babies go through 10 predictable mental leaps in the first 20 months of their life — periods of rapid neurological development during which the brain is reorganising, causing the characteristic fussiness, clinginess, and disrupted sleep that worry so many new parents.
The app generates a personalised leap calendar based on the baby’s due date, predicting when each leap will begin and end, which new skills may emerge from it, and how long the stormy phase is likely to last. Push notifications alert parents before a leap begins, giving them context for the difficult days ahead rather than leaving them wondering what has changed.
Rated 4.9 stars from over 109,000 App Store ratings and recommended by leading doctors, it is the best-selling app in its category and is available in 16 languages. A 24-month subscription costs around $34.99 and covers the entire first 20 months of a baby’s development.
Apps are frequently updated and may change over time. While we aim to keep our reviews accurate and up to date, some information may become outdated or no longer reflect the current version.
Disclaimer ▽ (click open)
How to Use
Setting up The Wonder Weeks requires entering the baby’s due date — not the birth date — as the leap schedule is calibrated from conception rather than delivery. This adjustment accounts for premature or post-due births and ensures the timing is as accurate as possible. Multiple children can be added, and the app links to a partner’s account so both parents track the same baby from their own phones.
The main screen shows a personalised leap calendar — a visual timeline of all 10 leaps colour-coded to indicate stormy periods (when fussiness is highest), sunny periods (calmer development phases), and the current position in the cycle. The app sends a push notification in the days before each leap begins, alerting parents that a difficult period is approaching and what it represents.
Tapping on any leap opens a detailed description of the mental development occurring during that phase: what the baby’s brain is reorganising, which new skills typically emerge, what behaviours to expect during the stormy period, and how to recognise the signs that the leap has started. Each leap includes 77 playtime games and activities designed to stimulate the skills being developed, with suggestions appropriate to the specific developmental stage.
A development diary allows parents to log milestones, notes, and observations. Optional add-ons include tracking of 350+ specific developmental milestones, a baby monitor, an e-book and audiobook of the original Wonder Weeks book, and curated lullabies. A community forum allows parents to share experiences and ask questions about specific leaps.
Strongest Points:
✓ Advance notifications before each leap begins give parents context and mental preparation for difficult periods before they start, reducing anxiety and self-doubt during stormy phases
✓ Based on decades of peer-reviewed research by developmental scientists, recommended by leading paediatricians, and used consistently by parents across multiple children with notable accuracy
✓ Rated 4.9 stars from over 109,000 App Store ratings — one of the highest-rated parenting apps available in any category
✓ Partner account linking means both parents, grandparents, and caregivers can access the same baby’s leap schedule and diary from separate devices simultaneously
✓ Includes 77 playtime games and activities tailored to each leap’s specific developmental stage, giving parents practical tools to support their baby’s growth during and after each phase
Weaker Points:
✕ The timing of leaps is not always precise to the day — individual babies may enter leaps slightly earlier or later than predicted, which can frustrate parents who expect exact timing
✕ Some users who paid for an early single-purchase version have reported frustration at being moved to a subscription model without being grandfathered into their original access
✕ The app’s interface can feel cluttered and navigating between sections is not always intuitive, particularly during the sleep-deprived early weeks when simplicity matters most
✕ The leap framework covers the first 20 months only — parents of toddlers beyond this age will need to look elsewhere for developmental guidance
✕ The development diary and milestone tracking features are less polished than the core leap calendar and have received mixed feedback from users who find them cumbersome to use
How to Use
Setting up The Wonder Weeks requires entering the baby’s due date — not the birth date — as the leap schedule is calibrated from conception rather than delivery. This adjustment accounts for premature or post-due births and ensures the timing is as accurate as possible. Multiple children can be added, and the app links to a partner’s account so both parents track the same baby from their own phones.
The main screen shows a personalised leap calendar — a visual timeline of all 10 leaps colour-coded to indicate stormy periods (when fussiness is highest), sunny periods (calmer development phases), and the current position in the cycle. The app sends a push notification in the days before each leap begins, alerting parents that a difficult period is approaching and what it represents.
Tapping on any leap opens a detailed description of the mental development occurring during that phase: what the baby’s brain is reorganising, which new skills typically emerge, what behaviours to expect during the stormy period, and how to recognise the signs that the leap has started. Each leap includes 77 playtime games and activities designed to stimulate the skills being developed, with suggestions appropriate to the specific developmental stage.
A development diary allows parents to log milestones, notes, and observations. Optional add-ons include tracking of 350+ specific developmental milestones, a baby monitor, an e-book and audiobook of the original Wonder Weeks book, and curated lullabies. A community forum allows parents to share experiences and ask questions about specific leaps.
Strongest Points:
✓ Advance notifications before each leap begins give parents context and mental preparation for difficult periods before they start, reducing anxiety and self-doubt during stormy phases
✓ Based on decades of peer-reviewed research by developmental scientists, recommended by leading paediatricians, and used consistently by parents across multiple children with notable accuracy
✓ Rated 4.9 stars from over 109,000 App Store ratings — one of the highest-rated parenting apps available in any category
✓ Partner account linking means both parents, grandparents, and caregivers can access the same baby’s leap schedule and diary from separate devices simultaneously
✓ Includes 77 playtime games and activities tailored to each leap’s specific developmental stage, giving parents practical tools to support their baby’s growth during and after each phase
Weaker Points:
✕ The timing of leaps is not always precise to the day — individual babies may enter leaps slightly earlier or later than predicted, which can frustrate parents who expect exact timing
✕ Some users who paid for an early single-purchase version have reported frustration at being moved to a subscription model without being grandfathered into their original access
✕ The app’s interface can feel cluttered and navigating between sections is not always intuitive, particularly during the sleep-deprived early weeks when simplicity matters most
✕ The leap framework covers the first 20 months only — parents of toddlers beyond this age will need to look elsewhere for developmental guidance
✕ The development diary and milestone tracking features are less polished than the core leap calendar and have received mixed feedback from users who find them cumbersome to use
Use it For:
👶 New parents in the first 20 months of their baby’s life who want to understand the developmental reason behind sudden fussiness, sleep disruption, and clinginess
🧠 Parents who want advance warning before difficult developmental phases so they can prepare emotionally and practically rather than being caught off guard
👪 Families where multiple caregivers — both parents, grandparents, nannies — want to stay informed about the baby’s developmental stage through linked accounts
🎮 Parents who want guided playtime ideas tailored to their baby’s specific developmental stage rather than generic age-based activity suggestions
📚 Anyone who has read or wants to read the Wonder Weeks book and wants the research presented in a personalised, interactive format updated to their baby’s actual timeline
App Usable on:
Phone
Tablet
PC
TV
Applications and Features
The central feature of The Wonder Weeks is its personalised leap calendar, generated from the baby’s due date. It maps all 10 mental leaps across the first 20 months with colour-coded stormy and sunny phases, advance timeline markers, and countdown notifications before each leap begins. Each of the 10 leaps is described in detail: the neurological changes occurring, the typical behavioural signals (increased crying, clinginess, sleep disruption), the new perceptual abilities the baby is gaining, and the skills that may begin to appear once the leap stabilises.
The 77 playtime activities included for each leap are suggestions for games and interactions that stimulate the specific skills being developed during that phase. These range from sensory play and object permanence games in early leaps to more language and relationship-based activities in later ones. The 350+ milestone tracker (available as an optional add-on) allows parents to log which specific skills have appeared, building a detailed developmental record over the 20 months.
The development diary accepts notes, observations, and photos. Cross-platform account sharing allows multiple caregivers to access the same baby’s profile. The community forum connects parents who are in the same leap simultaneously. A built-in baby monitor is available as an optional add-on. The app also bundles access to the e-book and audiobook versions of the original Wonder Weeks book, giving parents the full scientific background behind each leap.
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App Summary
The Wonder Weeks does something that almost no other parenting app does: it reduces anxiety rather than adding to it. By explaining in advance why a baby is about to become fussier, it converts a mystery that feels like failure into a predictable developmental process that feels manageable. The reviews across platforms are unusually consistent — parents describe using it with multiple children and finding it accurate enough to genuinely shift how they respond during difficult phases.
The 4.9-star App Store rating from over 109,000 reviews is one of the strongest signals of genuine satisfaction in the parenting app category, and the clinical and academic basis of the leap framework gives the app a credibility that most baby apps built on generic developmental timelines cannot match.
Its scope is limited by design: it covers the first 20 months and focuses specifically on mental development rather than physical milestones, sleep scheduling, feeding, or general baby tracking. For the specific thing it does — helping parents understand why their baby is struggling and what is coming next — it is the reference standard in its category.
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The Wonder Weeks uses a subscription model. A 24-month subscription costs around $34.99, which covers the full 20-month span of the leap framework and beyond. Shorter subscription options are also available. Optional add-ons include the 350+ milestone tracker, a baby monitor, e-book, audiobook, and curated lullabies, each available separately or as part of a bundle. The app does not have a permanent free tier.
Learning Difficulty:
The core experience requires nothing more than entering the due date — the leap calendar is generated automatically, and push notifications handle the timing, making it one of the most passive and low-effort developmental tools a parent can use.
Required Skill Sets:
Educational Content:
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Questions & Answers: ⮛ (click to open)
What is a mental leap and why does it make babies fussy?
A mental leap is a period of rapid neurological reorganisation in which a baby’s brain gains the ability to perceive and process the world in a more complex way. While this is a positive developmental event, the process is disorienting for the baby and disrupts their sense of familiarity and security. The result is the characteristic stormy behaviour that most parents recognise — increased crying, clinginess, feeding changes, and disrupted sleep — which typically lasts for a predictable number of days before resolving as the new skills consolidate.
Why does the app use the due date rather than the birth date?
The leap schedule is calibrated from the point of conception rather than delivery, because the neurological development that drives each leap begins before birth. Using the due date rather than the birth date ensures the timing is as accurate as possible, particularly for babies born two or more weeks early or late. Premature babies especially will follow a leap schedule that more closely matches their corrected age than their birth age.
Is The Wonder Weeks suitable for premature babies?
Yes. Because the app uses the due date for its calculations, it accounts for prematurity automatically. A baby born six weeks early will have their leap schedule set to their corrected age rather than their birth age, meaning the timing should remain relevant. Parents of premature babies should use the original due date when setting up the app for the most accurate results.
Does the app only track the 10 leaps, or does it do more?
The core function is the leap calendar and the leap-by-leap descriptions. The app also includes 77 playtime activity suggestions per leap, a development diary, a community forum, partner account linking, and optional add-ons for milestone tracking, a baby monitor, e-book, and audiobook. It is focused specifically on mental development in the first 20 months and does not track physical milestones, feeding, or sleep schedules in the way that dedicated baby tracker apps do.
Good to Knows: ⮛ (click to open)
• The app uses the baby’s due date, not the birth date, to calibrate the leap schedule — this is intentional and important for accuracy, particularly for babies born premature or post-term.
• Leap timing is predictive rather than exact — most parents find leaps begin within a few days of the predicted date, but individual variation is normal and the app itself notes that some babies enter leaps earlier than predicted.
• The app covers the first 20 months of development only — beyond that point, parents looking for continued developmental guidance will need to look to other resources as the app’s leap framework does not extend further.
Takeaways: ⮛ (click to open)
• The Wonder Weeks is the reference app for understanding a baby’s mental development in the first 20 months, built on genuine scientific research and consistently rated as the most accurate and useful tool in its category across multiple children.
• Its most valuable function is the advance leap notification — knowing a difficult phase is coming and why it is happening transforms the experience of the stormy weeks from confusion and self-doubt into something manageable and expected.
• At around $34.99 for 24 months it is one of the most cost-effective parenting tools available, covering the most challenging developmental period of a baby’s first two years for less than the cost of a typical book.
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