What are the sleep regression ages, and which are actually rough?

Hi Meg, “Sleep regression” is shorthand for indicating that something has changed with sleep, but there is no set timetable that every baby follows. The four-month regression is different. It reflects a biological shift as sleep matures and becomes more organised, rather than a short phase that simply passes. Later disruptions often coincide with developmental changes such as learning to roll, crawl, stand or walk, separation anxiety, teething, illness or changes to naps. This is why the ages most commonly talked about are around four months, eight to ten months, 12 months, 18 months and two years. Lots of typically developing children will be working on new skills at these points, or a nap transition may be on the cards. I would think of these as broad windows in which development may affect sleep, rather than fixed regression ages. The link between development and sleep disruption varies enormously between children. Some may seem completely unaffected, while others experience a significant setback. I would also avoid assuming that every difficult few nights must be a regression. Check for illness or discomfort, hunger, environmental changes, and whether their nap or bedtime needs may be shifting. Keep the bedtime routine and your responses as familiar and predictable as possible while you work out what is going on, rather than changing everything at once. If your baby seems uncomfortable, their feeding changes, or you have concerns about their breathing, health or development, speak to your health visitor or GP to rule out anything medical. I hope that helps!