The part nobody can time

Any number you are given for labour length depends entirely on where the counting starts, and the honest answer is that the first part cannot be measured.

The NHS on the latent stage: "It can take many hours, or even days, before you're in established labour. It's usually the longest stage of labour." Tommy's: "It can take hours or, for some people, days. This stage tends to be longer in a first pregnancy."

Tommy's is unusual in giving figures for it: "lasting an average of 9 to 12 hours" in a first pregnancy, and "around 7 to 9 hours" if you have been in labour before. Treat those as indicative rather than precise, because the start point of a latent phase is whatever the person in it decided it was.

NICE's definition explains why it resists measurement: the latent first stage is "a period of time, not necessarily continuous, when there are contractions and there is some cervical change, including cervical position, consistency, effacement and dilatation up to 4 cm". Something that stops and restarts cannot be timed with a stopwatch.

Established first stage: the figures with the most authority behind them

NICE's intrapartum guideline gives the numbers that UK maternity services work to. Recommendation 1.8.36 instructs staff to inform women that, while length varies:

First labours last on average 8 hours and are unlikely to last over 18 hours.
Second and subsequent labours last on average 5 hours and are unlikely to last over 12 hours.

The NHS phrases the same thing as a range: "In a 1st pregnancy, the time from the start of established labour to being fully dilated is usually 8 to 18 hours. It's often quicker (around 5 to 12 hours), in a 2nd or 3rd pregnancy."

Tommy's repeats it: "If you are having your first baby, the established phase tends to be around 8 hours, and rarely longer than 18 hours. If you have had a baby before it may well be shorter, lasting from around 5 hours to around 12 hours."

Three sources, one set of numbers, and they are measured from 4 cm — not from your first twinge.

The second stage

NICE separates a passive second stage, when the cervix is fully open but you are not actively pushing, from an active second stage. Its expectations for the active phase are:

First baby, no epidural: birth "would be expected to take place within 3 hours of the start of the active second stage in most women", with reassessment after 1 hour of active pushing and a senior review if birth is not imminent after 2 hours.
Second or later baby, no epidural: within 2 hours, with reassessment after 30 minutes and senior review if birth is not imminent after 1 hour.
With an epidural: the same 3-hour and 2-hour expectations, but preceded by a passive stage of up to 2 hours for a first baby, or up to 1 hour for later babies, before active pushing begins.

The NHS states it more simply: "If you're having your 1st baby, this pushing stage should last no longer than 3 hours. If you've had a baby before, it should take no more than 2 hours."

The third stage

Short, and with a defined limit. NICE: "Diagnose a prolonged third stage of labour if it is not completed within 30 minutes of the birth with active management or within 60 minutes of the birth with physiological management."

The NHS describes what usually happens: with active management the placenta "usually happens within 30 minutes of your baby being born"; with physiological management "it can take up to an hour for the placenta to come away, but it usually only takes a few minutes to push it out".

Why the whole-labour totals disagree

You will find two very different-looking figures quoted, and both are correct.

The HSE: "It is hard to know how long your labour will last, but most first babies arrive after 12 to 20 hours."

ACOG: "For a woman having her first baby, labor typically lasts 12 to 18 hours. For women who have given birth before, it typically lasts 8 to 10 hours."

Neither contradicts NICE. They are counting the latent phase as part of the total; NICE's 8 hours is established labour only. If you add a latent phase to NICE's figure you land in roughly the same territory. When someone quotes a number at you, the first question is where they started counting.

ACOG adds the caveat that belongs on every one of these figures: "But every woman is different. Your labor may not be like your mother's, your sister's, or your friend's labor. It may even be different with each child you have."

What makes it longer or shorter

National guidance is cautious here, and so is this list:

Whether you have given birth before. The one factor every source agrees on.
An epidural, which NICE notes "is associated with a longer second stage of labour and an increased chance of birth with forceps or ventouse".
The baby's position. The NHS lists an awkward position among the reasons labour can be slower than expected.
Movement and position. Tommy's states that moving around, staying upright and changing position "can increase your chance of a shorter labour", and that an upright position in the second stage "can help shorten the time you need to push for".
Interventions to speed things up. NICE notes that amniotomy after diagnosed delay "will shorten labour by about an hour".

What the numbers are actually for

They are not a prediction for you. They are the thresholds your midwife uses to decide when to look more closely.

NICE defines suspected delay in the established first stage as cervical dilatation of less than 2 cm in 4 hours, assessed alongside descent and rotation of the baby's head and changes in contractions. And it puts a limit on intervening for the sake of it: "Do not offer or advise clinical intervention if labour is progressing with no complications or concerns and the woman or pregnant person and baby are well."

A labour that is slower than average is not, by itself, a problem.

When to call someone

Your midwife or maternity unit when contractions come every 5 minutes or more often, or are regular, strong and lasting at least 60 seconds.
Urgently if your waters break, you have bleeding, your baby is moving less than usual, you are under 37 weeks, contractions last longer than 2 minutes, or you have 6 or more in 10 minutes (NHS).
Your midwife if a long latent phase is exhausting you. NICE says painful contractions without cervical change should be met with individualised support and analgesia if needed — you are allowed to ask.
Your local emergency number if you feel a strong urge to push and think the baby is coming.

The short version

Established first stage: about 8 hours for a first baby, unlikely over 18; about 5 hours for later babies, unlikely over 12. Active pushing: up to 3 hours first time, up to 2 after. Placenta: 30 minutes actively managed, 60 physiologically. The latent phase sits outside all of those numbers, which is why the totals you read elsewhere are longer.

How Long Labour Takes