Spend ten minutes in any pregnancy forum and you'll meet two different rules for "when labour is really happening": Americans talk about 411, while UK midwives talk about 3 in 10. They sound unrelated. They're actually two dialects describing the same moment — but the differences are worth knowing, especially if your antenatal class taught one and your birth unit uses the other.
Common in the US and Canada, 411 says labour is getting established when contractions are coming every 4 minutes, lasting 1 minute, and have kept that pattern up for 1 hour. (You'll also see 511 — every 5 minutes — as the earlier, more conservative trigger, especially for first babies, and some providers prefer it before heading to a hospital that's far away.)
Its strength is the third digit: the sustained for an hour requirement filters out the bursts of regular contractions that early labour loves to produce and then abandon.
Common in the UK, Ireland, Australia and New Zealand, this is how midwives themselves describe established labour: 3 to 4 contractions in every 10-minute window, typically lasting 45–60 seconds, strong enough that you can't talk through them. It's the language of triage calls — ring a British birth unit and you'll be asked how many contractions you're having "in ten minutes", not what your app's average interval is.
Its strength is observability: you don't need an hour of logging, just a focused 10-minute count, repeated when things change.
| 411 rule | 3-in-10 guideline | |
|---|---|---|
| Frequency | Every 4 minutes | 3–4 starts in 10 minutes (≈ every 2.5–3.5 min) |
| Duration | 1 minute | 45–60 seconds |
| Persistence | Sustained for 1 hour | Re-checked in repeated 10-min windows |
| Strength test | Implied ("real" contractions) | Explicit — can't talk through them |
| Mostly used in | US, Canada | UK, Ireland, AU, NZ |
Do the arithmetic and they converge: contractions every 3–4 minutes lasting about a minute. 3-in-10 is very slightly "later" (every ~3 minutes rather than every 4), and 411 demands an hour of consistency where 3-in-10 relies on the midwife re-checking with you over the phone. Neither is more correct — they're the same clinical picture phrased for different healthcare systems.
Frequency is measured start-to-start: from the beginning of one contraction to the beginning of the next. A 1-minute contraction every 4 minutes means 3 minutes of rest between them, not 4. Most timing mistakes — and most needlessly alarming app logs — come from measuring the gap instead.
Use whichever your care team speaks. If you'll be calling a UK-style birth unit, practise answering in 10-minute-window terms, because that's the question you'll be asked. If your provider taught you 411, count against that. And in every system the same caveats outrank any counting rule: call straight away about broken waters, bleeding, reduced movements, or labour signs before 37 weeks — whatever the stopwatch says.
If you'd rather not do stopwatch arithmetic between contractions, Tocos runs a midwife-style 10-minute check — tap each contraction's start and end, and the summary gives you count, average length and frequency in exactly the terms a triage call uses.
Tocos is a timing tool, not a medical device. It doesn't monitor your body or provide medical advice. Always follow the guidance of your midwife, doctor or birth unit, and contact them directly if you have any concerns.