For most expectant mothers, pregnancy lasts to full term, but sometimes baby unexpectedly arrives earlier. If your body goes into labour after week 20 but before week 37 of pregnancy it is called premature labour.
Around 8 in 100 babies will be born prematurely.
Call your midwife or maternity unit if you're less than 37 weeks pregnant and you experience any of the following:
- regular contractions or tightenings
- period-type pains
- a "show" – when the plug of mucus that has sealed the cervix during pregnancy comes away and out of the vagina
- a gush or trickle of fluid from your vagina – this could be your waters breaking
- backache that's not usual for you
The midwife or hospital will offer checks, tests and monitoring to find out whether:
- your waters have broken
- you're in labour
- you have an infection
These may include a vaginal examination, blood test, urine test and cardiotocography to record contractions and the baby's heartbeat.
They'll need to check you and your baby to find out whether you're in labour, and discuss your care choices with you.
What causes premature labour?
Many factors can contribute to preterm labor. Although the exact cause of preterm labor is unknown in many cases, one major cause is premature rupture of membranes (breaking the amniotic sac). Other related factors include the following:
- Preeclampsia (high blood pressure of pregnancy, which increases the risk of preterm delivery)
- Chronic medical illness (such as heart or kidney disease)
- Infection (such as group B streptococcus, urinary tract infections, vaginal infections, infections of the fetal / placental tissues)
- Drug abuse (such as cocaine)
- Abnormal structure of the uterus
- Cervical incompetence (inability of the cervix to stay closed during pregnancy)
- Previous preterm birth
Factors involving the pregnancy:
- Abnormal or decreased function of the placenta
- Placenta previa (low lying position of the placenta)
- Placental abruption (early detachment from the uterus)
- Premature rupture of membranes (amniotic sac)
- Hydramnios (too much amniotic fluid)
- Factors involving the foetus:
- When fetal behaviour indicates the intrauterine environment is not healthy
- Multiple gestation (twins, triplets, or more)
- Erythroblastosis fetalis (Rh/blood group incompatibility)
Planned premature labour
In some cases, pre-term labour is planned and induced because it's safer for the baby to be born sooner rather than later.
This could be because of a health condition in the mother, such as pre-eclampsia, or in the baby. Your midwife and doctor will discuss with you the benefits and risks of continuing with the pregnancy versus your baby being born premature.
You can still make a birth plan, and discuss your wishes with your birth partner, midwife and doctor.
If your waters have broken
If your waters have broken (called preterm pre-labour rupture of membranes, P-PROM), there's an increased risk of infection for you and your baby. You'll be offered:
- antibiotics to take for a maximum of 10 days, or until labour starts – whichever is sooner
- tests for infection, which may include blood and urine tests
P-PROM doesn't definitely mean you're going into labour. You may be able to go home if there's no infection and you don't go into labour within 48 hours. If you go home, you'll be advised to tell your midwife immediately if:
- your temperature is raised (a raised temperature is usually over 37.5C but check with your midwife – they may need you to call before it gets to 37.5C). You should take your temperature every 4 hours when you're awake
- any fluid coming from your vagina (called vaginal loss) is coloured or smelly
- you bleed from your vagina
- your baby's movements slow down or stop
If your waters haven't broken
Your midwife or doctor should discuss with you the symptoms of pre-term labour, and offer checks to see if you're in labour. These checks can include asking you about your medical and pregnancy history, and about possible labour signs, such as:
- contractions – how long, how strong and how far apart they are
- any pain
- vaginal loss, such as waters or a show
You may be offered a vaginal examination, and your pulse, blood pressure and temperature may also be checked.
Your midwife or doctor will also check your baby. They'll probably feel your bump to find out the baby's position and how far into your pelvis the baby's head is.
They should also ask about your baby's movements in the last 24 hours. If they don't ask, tell them about the baby's movements.
If you're in premature labour
The midwife or doctor may offer:
- medicine to try to slow down or stop your labour (tocolysis)
- corticosteroid injections, which can help your baby's lungs
Slowing down labour or stopping it isn't appropriate in all circumstances – your midwife or doctor can discuss your situation with you. They will consider:
- how many weeks pregnant you are
- whether it might be safer for the baby to be born – for example, if you have an infection or you're bleeding
- local neonatal (newborn) care facilities and whether you might need to be moved to another hospital
- your wishes
Corticosteroid injections can help your baby's lungs get ready for breathing if they're born prematurely. There are 2 injections, given 12 hours apart – your midwife or doctor will discuss the benefits and risks with you.
Corticosteroids probably won't be offered after 36 weeks as your baby's lungs are likely to be ready for breathing on their own.
If you're in premature labour and you're between 24 and 29 weeks pregnant you should be offered magnesium sulphate. This can help protect your baby's brain development. You may also be offered it if you're in labour between 30 and 34 weeks. This is to protect your baby against problems linked to being born too soon, such as cerebral palsy.
If you take magnesium sulphate for more than 5 to 7 days or several times during your pregnancy, your newborn baby may be offered extra checks. This is because prolonged use of magnesium sulphate in pregnancy has in rare cases been linked to bone problems in newborn babies.
What are the risks to my baby If born early?
Babies born before full term (before 37 weeks) are vulnerable to problems associated with being born premature. The earlier in the pregnancy a baby is born, the more vulnerable they are.
Babies are considered "viable" at 24 weeks of pregnancy – this means it's possible for them to survive being born at this stage.
Babies born this early need special care in a hospital with specialist facilities for premature babies. This is called a neonatal unit. Read more in our NICU - What to Expect article.
They may have health and development problems because they haven't fully developed in the womb.
If your baby is likely to be delivered early, you should be admitted to a hospital with a neonatal unit.
Not all hospitals have facilities for the care of very premature babies, so it may be necessary to transfer you and your baby to another unit, ideally before delivery (if time permits) or immediately afterwards.
Twins and multiples
Twins and triplets are often born prematurely. The average delivery date for twins is 37 weeks, and 33 weeks for triplets - reference NHS
57% chance of prematurity with a multiple pregnancy - reference Tommys.org
Find out more info on Twins