Premature birth: the basics
Pregnancy lasts an average of 40 weeks (usually between 38 and 42 weeks). A premature birth is when a baby is born before 37 weeks. So a baby born at 36 weeks and 6 days is officially premature.
The degree of prematurity is often described by gestational age as:
- extremely premature – from 22-28 weeks
- very premature – 28-32 weeks
- moderately premature – 32-34 weeks
- late preterm – 34-37 weeks.
Term babies are those born from 38 weeks.
Gestational age is the length of time your baby has been developing in your uterus. It’s calculated from the first day of your last period.
Exact gestational age is important because the more premature babies are, the less developed they’ll be. And this means that they’ll probably need more medical support for their lungs, hearts, tummy and bowels, temperature control and feeding.
For example, most babies who are born earlier than 32 weeks of pregnancy will need help with breathing. This means they’ll be cared for in a neonatal intensive care unit (NICU). If they’re more developed, they might be cared for in a special care nursery.
Low birth weight
Babies can be both premature and have low birth weight.
Low birth weight is when a baby’s weight is much lower than what’s expected for their gestational age.
Low birth weight can happen because premature babies are born before they get the chance to put on weight in the last weeks or months of pregnancy. These babies have low birth weight, but their development is usually appropriate for their gestational age.
How premature babies look
Your premature baby’s appearance depends quite a lot on how premature your baby is.
When a baby is born at 34-37 weeks of gestation (late preterm), they’ll probably look like a small term baby.
As a baby’s gestational age at birth decreases, their weight and size generally decrease too.
Extremely premature babies – for example, those born at 23 weeks of gestation – will be quite small and might fit snugly into your hand. They might look exhausted and have fragile, translucent skin. Their eyes might still be fused shut.
As these tiny babies grow, parents can watch the developmental changes in their baby’s appearance, movement and ability to interact with their world.
Premature birth: risk factors
In about half of all premature births, it isn’t known why the premature birth happens.
The following factors increase the likelihood of a premature birth:
- a previous premature birth
- some conditions of the uterus or cervix, like fibroids or a weakened cervix
- a multiple pregnancy – twins or more
- a maternal condition that means the birth needs to be brought on quickly for the safety of mother and baby – for example, pre-eclampsia
- conditions like diabetes and high blood pressure.
There are also other factors that are associated with premature birth. These include:
- not enough nutrition
- too much physical activity
- smoking, vaping or alcohol and other drug use
- too much stress
- anxiety or depression
- obesity or underweight
- lack of regular pregnancy care
- age – being under 17 years or over 35 years.
Minimising the risk of premature birth
The best way to make sure your pregnancy goes well is to go to your regular antenatal appointments and follow your doctor’s or midwife’s advice about:
- eating well and gaining the recommended weight
- not smoking or vaping, not drinking alcohol and not taking other drugs
- doing the recommended amount of physical activity
- managing stress, depression and anxiety.
Even if you follow all the pregnancy advice, you might still have a premature birth. But if you look after yourself, you’ll have done the very best you can for your baby. If you think you might be at risk of premature birth, talk to your doctor or other health professional.
Women who smoke or vape during pregnancy have a higher risk of having a baby with low birth weight, premature birth, miscarriage and stillbirth. Quitting, even just during pregnancy, will reduce the risk. If you need help to quit, talk to your doctor or midwife or call Quitline on 137 848.
Premature labour: signs and symptoms
Contact your midwife, doctor or hospital straight away if you notice one or more labour signs.
Also call your midwife, doctor or hospital as soon as possible if you notice any pregnancy health problems. It might be that you just don’t feel right, even though you don’t have any particular signs or symptoms. If this happens, trust your own instincts. See your doctor or midwife, or go to hospital.
If you’re in premature labour, the sooner you see a midwife or doctor the better. Some premature labours can be stopped or delayed. If your baby is growing well and getting all they need from your body, the longer your baby can stay in your womb, the better.
Sometimes you might know you’re going to have your baby early, so you can prepare for your premature birth. One way to prepare is by talking to your health professionals and asking some questions about premature birth.
Premature babies: survival and development
In Australia, most premature babies survive. And survival rates keep getting better as medical knowledge gets better.
Survival is affected by how premature a baby is. The more mature a baby is, the more likely they are to survive. Babies are also more likely to survive when they’re given the special care and equipment they need. For example, babies born after 23 weeks have a higher than 50% chance of survival if they’re born in a specialist maternity centre with a NICU.
Most premature babies go on to develop well. The longer your baby’s gestation, the less chance there is of any health or developmental concerns.
Babies who are born late preterm generally have no serious long-term problems.
Extremely premature babies (born at 28 weeks or less) have an increased risk of health and developmental problems. But even in extremely premature babies, severe health and developmental problems are quite uncommon.
Premature babies and their parents might have an unexpected and sometimes stressful start to their life together. But with expert care, support and guidance, the early problems often work out and most children develop well.