Premature birth: causes, care and what to expect

Pregnancy is usually around 40 weeks long. The NHS defines premature labour as labour before the 37th week, and babies born at that stage may need extra help because they have not finished developing in the womb. The earlier the birth, the more vulnerable the baby is likely to be.

NHS inform describes how premature babies are likely to be small and may have health issues, and notes that a baby born between 34 and 37 weeks can have the same issues as less mature babies even though they may be a good weight and look like a full-term baby.

Planned early births also happen. The NHS explains that in some cases pre-term labour is induced because it is safer for the baby to be born sooner, for example because of a health condition in the mother such as pre-eclampsia, or in the baby.

The NHS advises calling your midwife or maternity unit if you are less than 37 weeks pregnant and have any of these signs. You can also call if you are unsure or worried about anything.

• Regular contractions or tightenings.

• Period-type pains.

• A gush or trickle of fluid from the vagina, which could be your waters breaking.

• Backache that is not usual for you.

Tommy's says most of the time premature births happen spontaneously and doctors will often not know why, but some things are known to raise the risk. A previous premature birth makes it more likely again, and the more premature deliveries you have had, and the earlier they were, the higher the risk.

Tommy's also lists placenta praevia, placental abruption, polyhydramnios, differently shaped womb, vaginal bleeding, a weak cervix, carrying more than one baby, twin-to-twin transfusion syndrome, gestational diabetes, antiphospholipid syndrome, pre-eclampsia, waters breaking early, fetal growth restriction, obstetric cholestasis, infection of the membranes and urinary tract infections. It notes that previous treatment for abnormal cervical cells can also be a factor, and that pregnancy in the teens or over 40 carries a higher risk.

NHS inform says preterm rupture of membranes is the most common cause, and also lists infections, more than one baby and a weak cervix, adding that smoking, being overweight and an unhealthy diet make early birth more likely.

The NHS says the midwife or hospital will offer checks, tests and monitoring to find out whether your waters have broken, whether you are in labour and whether you have an infection. These may include a vaginal examination, a blood test, a urine test and cardiotocography, which records contractions and the baby's heartbeat. They will also ask about your baby's movements over the last 24 hours, so tell them about any change.

If your waters have broken before labour (called P-PROM), the NHS says there is an increased risk of infection, and you will be offered antibiotics and tests. It does not definitely mean you are going into labour, but you may be advised to stay in hospital for a few days. After going home you should call immediately if you have a raised temperature, greenish or smelly fluid, bleeding, tummy or back pain, contractions or reduced baby movements.

If you are in premature labour, the NHS says the midwife or doctor may offer medicine to try to slow or stop labour, steroid injections to help the baby's lungs, and medicine to help protect the baby's brain and nervous system. Slowing labour is not appropriate in every situation, and the team will consider how many weeks pregnant you are, whether it might be safer for the baby to be born, local neonatal facilities and your wishes.

The NHS says that between 24 and 29 weeks you should be offered magnesium sulphate through a drip, which can help protect the baby's brain development, and it may be offered at 30 to 33 weeks to protect against problems linked to being born too soon, such as cerebral palsy. Steroids may not be offered after 36 weeks as the baby's lungs are likely to be ready.

Some women are offered treatment to prevent early labour, for example if they have previously given birth before 34 weeks, had a late miscarriage, had waters break early before 37 weeks or had a cervical injury. The NHS says a vaginal scan between 16 and 24 weeks measures cervical length, and a cervix shorter than 25mm has been linked to higher risk. Options are a small vaginal hormone tablet or a stitch in the cervix, usually started before 24 weeks.

The NHS says it is possible for a baby to survive if born around 24 weeks of pregnancy onwards, and that babies born this early need special care in a hospital with specialist facilities, called a neonatal unit. Not all hospitals can care for very premature babies, so it may be necessary to transfer you and your baby to another unit.

NHS inform says babies born before 27 weeks need a hospital with a neonatal intensive care unit, and that for babies over 27 weeks doctors will advise where is best based on the level of care likely to be needed. Twins and other multiples are often born early, and a team monitors multiple pregnancies closely.

Staff keep parents informed and involved in decisions. Many units also offer support for parents.

NHS inform explains that the effects of being born early can last just a few days, until the baby reaches their due date, or can carry on affecting development throughout childhood. Every baby is different. All babies born early need time and extra help to adapt to life outside the womb.

The page lists areas where they may need help: starting to breathe, keeping warm, keeping breathing regular and oxygen levels normal, keeping blood sugar normal, clearing bilirubin (which causes jaundice) and fighting infection. Feeding can be slow. If a baby cannot take enough milk, a midwife or neonatal nurse can help you to use a breast pump or hand express milk until the baby is ready to feed.

Families should ask the neonatal team about follow-up plans, as development may be reviewed after discharge.

An early birth, and time on a neonatal unit, can be stressful, and parents may feel guilty even though early birth is rarely anyone's fault. Talk to the neonatal nurses, ask to be involved in care and consider contacting charities such as Bliss and Tommy's, which both offer information for families. Tell your GP or health visitor if low mood persists, because postnatal depression can follow a difficult birth.

If you have had a premature birth before, tell your midwife early in your next pregnancy so that a plan for monitoring and any preventive treatment can be made. On the NHS this care sits within maternity services. Anyone seeing a private obstetrician should make sure results are shared with the NHS maternity team too. Call 999 if you are bleeding heavily, in severe pain or the baby is coming.