Sleeping through the night means something much narrower than it sounds

Comparisons of the phrase sleeping through usually pick a winner. This one picks the circumstances, which is more useful.

Three different meanings

To most parents, sleeping through means going down in the evening and not being seen again until a civilised hour in the morning. To many relatives it means a baby who did not need attention during the hours they themselves were asleep, which is a shorter window.

In research it has often been defined as an uninterrupted stretch of a set number of hours, which may end well before dawn. A baby sleeping from seven until one in the morning satisfies some of those definitions and none of a parent's hopes. When three people use the same phrase for three different things, comparison between them is meaningless, which is worth knowing before the next conversation.

Why the anecdotes do not match

The stories that circulate are almost never accompanied by definitions, timings, or an acknowledgement of the weeks that went differently. Retelling also shortens things, and a baby who slept through twice at ten weeks becomes a baby who slept through from ten weeks. Parents whose babies do it early are also more likely to mention it, which skews the sample you personally encounter.

None of this involves anyone lying; it is the ordinary compression that happens to any story told repeatedly. Assuming the reality behind any such account is messier than the version you heard is usually accurate.

It is not a permanent state

Babies who achieve long stretches frequently stop again, often during illness, travel, teeth or a developmental period. That means sleeping through is better understood as something that happens on some nights than as a threshold that is crossed. Parents who treat it as a switch experience each return to waking as a loss, which is unnecessarily discouraging.

Treating it as a rising average across months rather than an event makes the actual trajectory much easier to see. By the end of the first year most babies are doing longer stretches than they were at three months, with a great deal of variation in between.

What the research picture looks like

Studies of infant sleep generally find wide variation, high rates of night waking through the first year, and considerable differences depending on how questions are asked. Parent-reported waking and objectively measured waking do not always agree, partly because babies surface without their parents noticing.

Around the four-month mark, that gap is genuinely interesting, because it suggests some of what changes over the year is whether waking requires a parent rather than whether it happens. Precise figures vary by study, definition and country, so quoting one as a benchmark would be misleading.

The reliable summary is that frequent waking in the first year is common enough to be unremarkable to the professionals who see it.

Talking about it with other people

The most useful defence is asking what somebody means when they use the phrase, which usually ends the comparison politely. It is also entirely reasonable to decline the conversation, since almost nothing useful comes out of comparing infant sleep between households. Relatives asking whether the baby is good yet are asking about sleep, and the question deserves a bland answer rather than an honest one.

Among friends with babies, the more useful conversation is about how the adults are coping rather than about the numbers. The families who find the first year hardest are frequently the ones spending the most time measuring themselves against other people's accounts.

Milestone ranges are wide, and where one baby sits inside a range says very little on its own.

A better measure

A more useful question than whether the baby sleeps through is whether each adult in the house is getting one decent block of sleep. That is something you can actually change, through shifts, daytime cover and asking for help, none of which depend on the baby. It also avoids handing the household's sense of how things are going to something entirely outside its control.

In the small hours, if the honest answer is that neither adult is getting a block, that is the thing to raise with a health visitor. Sleep in the first year is a household resource-allocation problem far more often than it is an infant behaviour problem.

Side by side

The takeaway

Ask people what they mean by the phrase, then stop using it, and measure whether the adults are getting a block instead.

Nothing in the first year lasts, including the parts that feel permanent at three in the morning.