Preterm birth is more common than most people expect. The WHO estimates that 13.4 million babies were born before 37 weeks in 2020, more than one in ten of all births, and in the UK the NHS puts it at about 8 in every 100. Complications of prematurity are the leading cause of death in children under five worldwide. The single most useful thing you can know is what preterm labour feels like, because the treatments that change the outcome — steroids for the lungs, magnesium for the brain — only work if there is time to give them.
This guide covers the signs that matter before 37 weeks, how they differ from the practice contractions of late pregnancy, what actually happens when you call, and what the hospital can do in the first hours. It also covers who is at higher risk and what is offered to lower it, because for some women preterm labour is predictable months in advance.
The short answer. Before 37 weeks, call your maternity unit the same day, not tomorrow, if you have regular contractions or tightenings, period-type pain, a low backache that is new for you, a gush or trickle of fluid, or a change in discharge — watery, mucus-like, pink or bloody. Do not wait to see whether it settles. If it is preterm labour, steroids given early cut the baby's risk of breathing problems and death; if it is not, you have lost an afternoon.
The Signs to Act On
| Sign | What it feels like | What to do |
|---|---|---|
| Regular tightenings or contractions | The bump goes hard, then softens, at intervals that stay regular or get closer. May or may not hurt. | Rest, drink a glass of water, note the times. If they keep coming, call. |
| Period-type pain or cramps | A low, dull ache like the first day of a period, constant or in waves. | Call the same day. |
| A new low backache | Dull pain across the lower back that is not your usual pregnancy back pain and does not ease with position. | Call the same day. |
| Fluid from the vagina | A gush or a steady trickle you cannot control, clear or straw-coloured. | Put on a pad, note the colour, call now. See water breaking. |
| A change in discharge | Suddenly more, watery, mucus-like, pink-tinged or streaked with blood. | Call the same day. See discharge in pregnancy. |
| Pelvic pressure | A heavy feeling low down, as if the baby is pushing downwards. | Call the same day, especially with any of the above. |
None of these needs to be dramatic. Preterm labour often starts quietly, and women who have been through it describe the tightenings as mild and the backache as "not that bad" right up to the point where the cervix had already changed. The instruction is to call on the pattern, not the intensity.
Preterm Labour or Braxton Hicks?
From the middle of pregnancy the uterus practises with Braxton Hicks contractions: irregular, painless or mildly uncomfortable, and they fade when you change position, rest and drink. Our Braxton Hicks guide covers the twenty-minute test that settles most cases at term.
Before 37 weeks the same test applies, but the bar is lower. Lie on your left side, drink a large glass of water, and time them. If they are still coming at regular intervals after that, or they get closer, or any pain, fluid or bleeding joins in, stop testing and call. The cost of a false alarm is an evening on a monitor; the cost of waiting is the window in which steroids work.
What Happens When You Call
1. Assessment
You will be asked to come in. A midwife or doctor will feel the bump, put you on a CTG monitor that traces the contractions and the baby's heartbeat, and usually look at the cervix with a speculum to check for fluid or opening. A urine sample is tested, because a urine infection can itself trigger tightenings.
2. Deciding whether this is real
From 30 weeks, NICE guidance uses one of two tests to decide how likely labour is in the next few days: a transvaginal scan of the cervical length, or a fetal fibronectin swab. A long cervix or a negative swab means labour is unlikely and you will usually be monitored and sent home. Before 30 weeks the decision is made on the examination alone, and doctors err on the side of treating.
3. If it is preterm labour
- Steroid injections. Offered from 24 weeks to 33 weeks and 6 days, and considered up to 35 weeks and 6 days, to mature the baby's lungs. A Cochrane review of 14 studies found they cut the risk of death around birth by about 15% and of respiratory distress syndrome by about 29%. After 36 weeks they are usually not offered because the lungs are ready.
- Magnesium sulfate. A drip given in the 24 hours before a very preterm birth to protect the baby's brain and lower the risk of cerebral palsy. Offered from 24 weeks to 29 weeks and 6 days, considered up to 33 weeks and 6 days.
- Holding labour off. A medicine such as nifedipine can delay contractions for a short window — enough for the steroids to work and for a transfer to a hospital with the right level of neonatal care. It does not stop established labour for good.
- Antibiotics if your waters have broken. Erythromycin is given for up to ten days to lower the infection risk while the pregnancy continues.
- Transfer. If your hospital does not have the neonatal unit a baby of this age needs, you may be moved before the birth rather than the baby being moved after it.
Bring your notes, your hospital bag if it is packed, and the times you wrote down. If it is not packed, do not stop to pack it.
Who Is at Higher Risk
Most preterm labour happens to women with no risk factor at all, which is why the signs matter for everyone. But some things raise the odds, and they change what your antenatal care should include:
- A previous preterm birth or a loss after 16 weeks.
- A short cervix on a scan between 16 and 24 weeks.
- Twins or triplets.
- Previous cervical surgery, such as a LLETZ or cone biopsy.
- Infections — urine infections and bacterial vaginosis in particular.
- Smoking, and a short gap since the last pregnancy.
- Complications such as pre-eclampsia or growth restriction, where the birth is brought forward on purpose.
What Is Offered to Prevent It
If you have a history: ask at booking for a plan. NICE says that a woman with both a previous preterm birth or late loss and a cervix of 25 mm or less on a scan at 16 to 24 weeks should be offered a choice of vaginal progesterone or a cervical stitch (cerclage); with either factor alone, progesterone should be considered. Progesterone runs from 16 to 24 weeks until at least 34.
Beyond that, the useful steps are unglamorous: get urine infections treated promptly rather than waiting them out, stop smoking, and keep antenatal appointments so that blood pressure and growth are checked. What does not help is bed rest, which has not been shown to prevent preterm birth and is not recommended in current guidance — it brings clot risk and muscle loss without buying any weeks.
If Your Baby Is Born Early
What a preterm baby needs depends almost entirely on the week. Babies born at 34 to 36 weeks are often on the postnatal ward with you, needing help with feeding and keeping warm. Babies born earlier go to a neonatal unit, where the care ranges from a warm cot and tube feeding to intensive care for the smallest. Ask the unit to explain their plan for your baby's gestation specifically, because the general picture is far bleaker than the picture for a baby at 33 weeks who has had steroids.
Kick counting continues to matter: a change in your baby's usual pattern of movements is a same-day call at any gestation from 28 weeks, and reduced movements sometimes precede preterm labour.
When to Call
Before 37 weeks, call your maternity unit the same day if: you have regular tightenings that continue after rest and a drink; period-type pain or a new low backache; a gush or trickle of fluid; a change in discharge, especially pink or bloody; pelvic pressure; or a change in your baby's movements.
Call emergency services or go straight in if: you are bleeding heavily, you can feel or see the cord, or you feel the urge to push. If your waters have gone and the fluid is green or brown, say so when you call.
At a Glance
More than one in ten babies worldwide is born before 37 weeks. The signs to act on are regular tightenings, period-type pain, a new low backache, fluid, a change in discharge and pelvic pressure — call on the pattern, not the intensity, and do not wait to see whether it settles. At the hospital a cervical length scan or fibronectin swab decides how likely labour is; if it is likely, steroids from 24 weeks mature the lungs and magnesium before 30 weeks protects the brain, and both need hours to work. Women with a previous preterm birth or a short cervix should have a progesterone or stitch plan from mid-pregnancy. Bed rest does not help.
Inside Baby Novum. The contraction timer logs each tightening's length and the interval between them, so when the unit asks "how often and for how long" you have the answer on your phone rather than a guess. The 5-1-1 alert is built for term; before 37 weeks, the pattern in the log is what matters. The kick counter runs from week 28 with a daily reminder.
Next: Braxton Hicks vs Real Contractions → · Water Breaking → · Signs of Labour →
Frequently Asked Questions
What counts as preterm labour?
Labour that starts before 37 completed weeks of pregnancy. The WHO splits it into extremely preterm (before 28 weeks), very preterm (28 to 32 weeks) and moderate to late preterm (32 to 37 weeks). From 37 weeks and 0 days a baby is term, and the same signs mean labour rather than preterm labour.
How do I tell preterm labour from Braxton Hicks?
Braxton Hicks are irregular, do not build, and usually ease when you change position, rest and drink. Preterm labour contractions come at regular intervals, get closer and stronger, and often bring period-type pain, a low backache that is new for you, pelvic pressure or a change in discharge. Before 37 weeks the bar is lower: if regular tightenings keep coming after you have rested and had a drink, call.
How many contractions do I need before I call?
Do not count to a threshold before 37 weeks. The 5-1-1 rule is for term labour. Regular tightenings that keep coming, any tightening with pain, fluid or bleeding, or a change you cannot explain are each enough on their own to call your maternity unit now, not in the morning.
What happens when I get to the hospital?
A midwife or doctor will examine you, put you on a monitor to trace the contractions and the baby's heartbeat, and usually look at the cervix with a speculum. From 30 weeks a cervical length scan or a fetal fibronectin swab helps decide whether labour is really likely in the next days; before 30 weeks the decision is made on the examination alone. Many women are monitored and sent home when it settles.
What do the steroid injections actually do?
They speed up the maturing of the baby's lungs. A Cochrane review found that antenatal corticosteroids cut the risk of a baby dying around birth by about 15% and the risk of respiratory distress syndrome by about 29%. NICE says to offer them from 24 weeks to 33 weeks and 6 days and to consider them up to 35 weeks and 6 days, which is why an early call matters: the injections need time to work.
What is the magnesium drip for?
Protecting the baby's brain. Magnesium sulfate given shortly before a very preterm birth lowers the risk of cerebral palsy. It is offered between 24 weeks and 29 weeks and 6 days and considered up to 33 weeks and 6 days, as a drip in the 24 hours before the birth is expected.
Can preterm labour be stopped?
Sometimes it stops on its own, and threatened preterm labour that settles is common. If it does not, a medicine such as nifedipine can hold contractions off for a short window — long enough for the steroids to work and for you to be transferred to a unit with the right neonatal care — but it does not stop established labour for good.
Can I prevent preterm labour?
If you have had a preterm birth or a late loss before, or a scan between 16 and 24 weeks shows a cervix of 25 mm or less, you should be offered vaginal progesterone or a cervical stitch. Treating urine infections promptly and stopping smoking both help. Bed rest has not been shown to help and is not recommended.