The 10 fussy “leap” periods parents often talk about: when they start, how long they last and what you may notice. Enter the due date to see your baby's dates.
Last updated: October 2026.
Weeks are counted from the due date. Enter it and each leap's dates appear in the chart; the date never leaves your device.
| Leap | What changes | Weeks |
|---|---|---|
| Leap 1 | Sharper sensesAbout 1 month old, lasts about 1 week | 4.5–5.5 |
| Leap 2 | Noticing repetitionAbout 2 months old, lasts about 2 weeks | 7.5–9.5 |
| Leap 3 | Smooth transitionsAbout 3 months old, lasts about 1 week | 11.5–12.5 |
| Leap 4 | Events and results3.5–4.5 months old, lasts about 5 weeks | 14.5–19.5 |
| Leap 5 | Distance and separation5–6 months old, lasts about 4 weeks | 22.5–26.5 |
| Leap 6 | Grouping and recognizingAround 8 months old, lasts about 4 weeks | 33.5–37.5 |
| Leap 7 | Step by step9.5–10.5 months old, lasts about 5 weeks | 41.5–46.5 |
| Leap 8 | Goal-directed plansAround 1 year old, lasts about 4 weeks | 50.5–54.5 |
| Leap 9 | Flexibility and choiceAround 14 months old, lasts about 5 weeks | 59.5–64.5 |
| Leap 10 | Self and rules16–17 months old, lasts about 5 weeks | 70.5–75.5 |
In each leap your baby starts to perceive the world in a new way. The fussiness passes; a new skill often follows at the end.
Your baby's senses develop quickly and they become more sensitive to light, sound and touch. More crying, more frequent feeding and wanting to be held are common. A calm, dim room and skin-to-skin contact help. By the end you may notice them staying awake longer and looking around.
Your baby starts noticing simple repetition in hands, feet, sounds and shapes. Sleep and feeding may be disrupted and they may be clingier. Let them explore their hands and try out new sounds; echoing the sounds they make draws them into a conversation.
Movements and voice become smoother, and your baby notices transitions such as light fading or a sound getting louder. It is a short phase; a few days of fussiness and frequent feeding may occur. Rocking them slowly or singing softer and louder suits this new interest.
Your baby perceives sequences of movement as events and starts noticing that actions have results. It is a long phase and often coincides with changes in sleep; it overlaps with what many parents call the “4-month sleep regression”. Cause-and-effect games such as rattles and rolling balls catch their interest.
Your baby begins to grasp the distance between people and things, and notices that you can move away. Separation anxiety, shyness with strangers and night waking may increase. Short goodbyes and peekaboo make this phase easier.
Your baby starts grouping similar things: animals, foods, people. Comparing and telling things apart catches their interest. Fussiness, clinginess and sleep changes may appear; name the things around them as you go.
Your baby discovers doing the steps of a task in order, like picking up a spoon and bringing it to the mouth or putting a block in a box. Because they want to do it themselves, frustration and protests may increase. Give them time and chances with small tasks.
Your child combines simple steps to reach a goal and notices that the same goal can be reached in different ways. Stubbornness and tantrums may begin. Offering choices and keeping daily routines help.
Your child learns to change plans to fit the situation, to experiment and to imitate, and tests limits. Mood swings may be noticeable. Consistent, calm limits give them security.
Your child realizes more clearly that they are a separate person; “me” and “mine” become clear and they begin to understand family rules. Stubbornness, jealousy and wanting to be held may increase; patience and consistency are key in this phase.
The common signs last a few days and usually pass on their own by the end of the leap:
From the due date. Leaps are thought to follow brain development, so time in the womb counts too: in a baby born 2 weeks early, leaps start about 2 weeks later than the birth date suggests, and in a baby born 1 week late, 1 week earlier. If you don't know the due date, the date of birth gives an approximate result.
It depends on the leap: leaps 1 and 3 last about a week, leap 2 about two weeks, and leap 4 onwards can last 4–5 weeks. Fussiness usually shows during part of the period rather than all of it.
Leaps don't cause fever. If your baby has a temperature of 38 °C (100.4 °F) or higher, refuses to feed, has clearly fewer wet nappies, vomits, has diarrhoea, struggles to breathe, is unusually floppy or drowsy, or has a high-pitched cry you can't settle, don't put it down to a leap: contact your doctor. In babies under 3 months, any fever needs to be checked right away.
Leaps are based on observations of infants by the Dutch researchers Hetty van de Rijt and Frans Plooij, and they are very popular with parents. But independent research has not firmly shown that these periods happen in the same weeks for every baby. Use the chart as a guide: your baby may not be fussy in these weeks, or may be fussy at other times.
Lots of cuddles and skin-to-skin contact, feeding on demand, keeping bedtime routines and simple games that match their new interest all help. Leaps are tiring for parents too; asking for help so you can rest is fine.
This page is for information only and is not medical advice. Follow your doctor's advice for decisions about your baby's health.
Agu works out leaps from the due date, reminds you as each one starts and shows the leap that falls in each week of its week-by-week development guide. No account, no ads, no internet.
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