If you ring a birth unit in the UK and many other countries, the midwife on the phone is quietly measuring your answer against one yardstick: how many contractions you're having in every 10 minutes, how long each one lasts, and how strong they feel. The common rule of thumb for established labour is 3 to 4 contractions in 10 minutes, each lasting around 45 to 60 seconds, strong enough that you can't talk through them.
That's often shortened to "3 in 10" — and it's worth understanding properly, because it's the difference between being asked to come in and being gently told to stay home a little longer.
The guideline combines three separate things, and all three matter:
Frequency. Count the number of contractions that start within a 10-minute window. Three contractions starting in 10 minutes works out to one roughly every 3 minutes or so. Note that frequency is measured from the start of one contraction to the start of the next — not from the end of one to the start of the next.
Duration. How long each contraction lasts, from the moment you feel it building to the moment it fully releases. In established labour, contractions typically last 45–60 seconds. Early labour contractions are often shorter — 20 or 30 seconds — even when they feel intense.
Strength. The hardest to measure and the most telling. The classic markers: you have to stop what you're doing, you can't hold a conversation through the peak, and you need to actively breathe or move through each one. A contraction you can chat through is almost certainly not established labour, regardless of how frequent it is.
Midwives assess contractions over a fixed observation window because labour is noisy data. Contractions cluster, space out, pause when you change rooms or get in the car, and pick up again. A single 10-minute observation, repeated when things change, gives a far clearer picture than hours of obsessive logging — and obsessive logging is genuinely counterproductive in early labour, when the best thing you can do is rest, eat, and ignore it as long as you can.
That's also exactly how a midwife on a triage call will phrase it: "In the last 10 minutes, how many did you have?" If you've just done a timed 10-minute check, you can answer in one sentence.
Early (latent) labour can run for hours — sometimes days — with irregular contractions that come every 5, 10 or 20 minutes. This is normal and useful: your body is doing real work. The general advice for an uncomplicated pregnancy is to stay home, rest, eat and drink, use a bath or TENS machine, and re-check with a timed window when things feel like they've changed gear.
It's also normal for contractions to briefly become less frequent. One quiet 10-minute window doesn't mean labour has stopped — repeat the check after a while rather than reading too much into a single observation.
The 3-in-10 yardstick only applies to contraction timing. Call your midwife or birth unit straight away — whatever your contractions are doing — if your waters break (especially if the fluid is green, brown or bloodstained), if you notice bleeding, if your baby's movements change or reduce, if you're under 37 weeks, or if anything at all feels wrong to you. Maternity units always prefer a call that turns out to be nothing over the reverse.
You can do a 10-minute check with the clock on your oven: note each time a contraction starts and ends, then count. If you'd rather tap a button than do arithmetic at 3am, Tocos is a simple timer built around exactly this check — a 10-minute window, one tap at the start and end of each contraction, and a summary you can read straight down the phone.
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.