Baby Sleep at 9 to 12 Months: The Complete Guide to This Busy Stage

The period from 9 to 12 months marks the transition from "older baby" to "almost toddler," and the changes happening are remarkable — every one of which can affect sleep.

Physically: This is the age of mobility. Pulling to stand is typically mastered between 9 and 11 months. Cruising (walking while holding furniture) usually begins around 9 to 12 months. Some babies take their first independent steps — though the average is around 12 months, with enormous normal variation (not walking by 18 months is the point at which to consult your GP). Your baby may crawl confidently, or they may skip crawling entirely and shuffle, commando-crawl, or go straight to standing. All are normal variants.

Cognitively: Object permanence is now fully established. Your baby completely understands that you exist when you leave the room — and they do not like it. Problem-solving is emerging: they can figure out how to reach things, open containers, and "work the system" at bedtime by calling, standing, and throwing things from the cot. Language comprehension is accelerating — by 12 months, most babies understand 50 to 100 words even if they only say 1 to 5.

Emotionally: Separation anxiety typically peaks between 10 and 18 months. This is the most intense period — your baby may become extremely clingy, cry when you leave the room briefly, and protest vigorously at bedtime. This is developmentally driven and is a sign of secure attachment, not a behaviour problem.

Feeding: Solids are now a significant part of the diet — your baby is likely having 3 meals and 1 to 2 snacks alongside milk feeds. As they approach 12 months, the transition from formula to whole cow's milk can begin (NHS guidance). Breast milk can continue for as long as mum and baby wish.

Most babies at this age need approximately 12 to 14 hours of total sleep in 24 hours, with around 10 to 12 hours at night and 2 to 3 hours during the day across 2 naps.

Wake windows are continuing to extend:

• At 9 to 10 months: approximately 3 to 3.5 hours between sleeps
• At 11 to 12 months: approximately 3.5 to 4 hours, with the longest wake window before bedtime often approaching 4 hours

As always, these are averages from population studies, not prescriptions for your individual baby. BASIS (Durham University) emphasises the huge underlying variation in how much babies sleep. A baby consistently sleeping 12 hours total may be perfectly well-rested. Your baby's mood, development, and overall wellbeing are better indicators than total hours.

Your baby should remain on 2 naps throughout this entire period. This is important to emphasise because many parents see nap resistance around 12 months and assume it is time to drop to one nap. In most cases, it is not — the 2-to-1 nap transition typically happens between 14 and 18 months. Dropping to one nap at 12 months usually leads to chronic overtiredness and worse night sleep.

A single refused nap does not mean your baby is ready to transition. It may be caused by teething, developmental changes, or simply undertiredness on that particular day. Look for a consistent pattern over 2 or more weeks before making schedule changes.

This is perhaps the most iconic sleep challenge of the 9 to 12 month period. Your baby pulls to stand, grips the cot bars, and cries — either because they genuinely cannot get back down, or because standing is far more interesting than sleeping. It is one of the most common concerns parents Google at this age, and it is a phase that passes.

What helps:

• Practise during the day. Help your baby learn to lower themselves from standing to sitting to lying. Practise at the sofa, at the cot during non-sleep times, at play gyms. The more they master the skill while awake, the less compelled they are to practise at night
• Calm, consistent response at sleep time. When your baby stands in the cot, gently and calmly lay them back down. Use a brief, boring phrase — "Time to lie down, night-night" — and avoid making it a game. Repeat as many times as needed. Some parents report doing this 20 to 30 times on the first night, but it reduces rapidly
• Do not engage. Keep the room dark, your voice quiet, your interactions brief. Prolonged eye contact, conversation, or play rewards the standing behaviour and makes it harder to stop
• Ensure the mattress is at the lowest setting. This is a safety essential once your baby can pull to stand — they can topple over higher cot sides

This phase typically resolves within 1 to 2 weeks once the skill is well practised during the day. Your baby is not being defiant. They are experiencing a compulsion to practise a new motor skill, and that compulsion is strongest when they are in the one place where there are vertical bars to grab.

The 12-month regression — which can arrive anywhere between 11 and 13 months — is driven by a convergence of developmental changes that all happen to peak around your baby's first birthday.

• Motor overload: Pulling to stand, cruising, and first steps create enormous physical restlessness. Your baby may cruise along the cot bars or attempt to climb
• Separation anxiety at its peak: Object permanence is fully developed, and your baby's emotional response to separation is at its most intense. Bedtime can become a battleground
• Nap resistance: Some babies begin refusing one of their two naps. In most cases, this does not mean they are ready for one nap. Dropping to one nap at 12 months typically makes things worse
• First birthday changes: The transition from formula to cow's milk, routine shifts, and sometimes a parent returning to work can all contribute
• Language explosion: The brain is processing new words and concepts at a remarkable rate, which can increase overnight restlessness

This regression typically lasts 2 to 6 weeks. The key principles during this period:

• Maintain your consistent bedtime routine
• Provide plenty of opportunities to practise new physical skills during the day
• Resist dropping to one nap — keep offering two naps and accept that some days one will be refused
• Avoid introducing new sleep habits that will be difficult to sustain (bringing baby into your bed for the first time, starting new feeding patterns)
• An earlier bedtime on particularly rough days is nearly always helpful

Some babies still benefit from one night feed at this age, particularly breastfed babies. This is normal and is not something to feel guilty about.

As your baby approaches 12 months, night feeds are typically no longer nutritionally necessary for most babies — though some health visitors may advise differently for babies who are underweight or have other health considerations. The key is that any reduction is gradual, not abrupt.

If your baby is waking multiple times and feeding back to sleep each time, it is worth considering whether this is hunger or a sleep association. Some indicators:

• Genuine hunger: Active feeding — gulping, swallowing for several minutes, taking a full feed. The baby is genuinely hungry and needs the calories
• Sleep association: Brief comfort-suck, a few minutes at most, baby falls straight back to sleep. The feeding is functioning as a way to get back to sleep, not as nutrition

Neither is "wrong." Feeding to sleep is biologically normal and only needs changing if it is unsustainable for your family. If multiple night feeds are leaving you chronically sleep-deprived and you want to make changes, that is a valid choice. If you are managing fine, there is no rush.

Ensuring adequate daytime nutrition — 3 meals, 1 to 2 snacks, and sufficient milk feeds during the day — supports a gradual, natural reduction in night feeding. Iron-rich foods are particularly important at this age, as iron deficiency has been linked to restless sleep.

If you are concerned about your baby's feeding, weight gain, or nutritional intake, speak to your health visitor or GP. This is sleep support, not dietary advice.

Most babies are not ready to transition from 2 naps to 1 until between 14 and 18 months (average around 15 months). This is important to state clearly because the 12-month regression commonly causes nap refusal that many parents interpret as readiness — and dropping too early is one of the most common causes of chronic overtiredness in the 12 to 18 month age range.

Signs of genuine readiness (which must be present consistently for 2 or more weeks, not intermittently):

• Consistently refusing one nap or taking a very long time to fall asleep for it
• The second nap pushes so late that bedtime is being delayed
• Night sleep is being disrupted (split nights, early morning waking)
• Your baby can comfortably handle a 5-hour wake window without falling apart

If your 12-month-old is fighting one nap but does not meet these criteria consistently, the more likely explanation is the 12-month regression. Continue offering two naps. Adjust wake windows by 15 to 30 minutes. Cap the first nap at 1 hour 15 minutes if it is running long and stealing sleep pressure from the second. And bring bedtime earlier on days when the second nap is refused.

The 2-to-1 transition, when it does come, takes 2 to 4 weeks and is often messy. Some days will still need two naps. Earlier bedtimes on single-nap days are essential. It is a process, not a switch.

Normal at this age:

• 1 to 2 night wakings that settle with brief reassurance or a feed
• Some nights better than others
• Standing in the cot and needing help to lie back down
• Intense protest at bedtime during separation anxiety peaks
• Occasional nap refusal, particularly around 12 months
• Fussiness and disrupted sleep for 2 to 3 days around active teething
• Taking 10 to 20 minutes to fall asleep

Worth speaking to your GP or health visitor about:

• Persistent waking every 30 to 60 minutes all night, every night, for more than 2 to 3 weeks
• A sudden dramatic change in sleep with no obvious cause
• Extreme distress that pain relief does not ease — could indicate an ear infection or other illness
• Persistent snoring, mouth breathing, or pauses in breathing during sleep (possible sleep apnoea)
• Fever above 38 degrees Celsius, diarrhoea, or rash attributed to "teething" — these are not teething symptoms according to the NHS
• Not meeting any motor milestones (not sitting, no attempt at mobility by 9 months)

Many 12-month-olds still wake 1 to 2 times per night, and this is within the normal range. "Sleeping through" is a wide spectrum — even adults wake briefly between sleep cycles. If your baby is developing well, generally happy during the day, and managing their wake windows without major meltdowns, their sleep is most likely appropriate for their age.

If you are worried about your baby's health or development, speak to your GP or health visitor. This is sleep support, not medical advice.