Premature birth: the basics

Pregnancy lasts an average of 40 weeks (normally 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 23-28 weeks
• very premature – 28-32 weeks
• moderately premature – 32-36 weeks
• late preterm – 36-37 weeks.

Gestational age
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 more premature babies won’t be as developed and will probably need more medical support for their lungs, hearts, tummy and bowels, temperature control and feeding.

For example, most babies who are born at less 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 (SCN).

Low birth weight
Babies can be both premature and low birth weight.

Low birth weight is when babies weigh less than 2.5 kg.

Low birth weight can happen because premature babies don’t get the chance to put on weight in the last weeks or months of pregnancy. These babies have low birth weight but are the appropriate size for their gestational age.

Low birth weight can also happen when, for some reason, babies can’t grow as much as usual in the womb, making them small for their gestational age. These babies have a birth weight at or below the lowest 10th percentile for their gestational age.

How premature babies look

How your premature baby’s body looks depends quite a lot on how premature she is.

When a baby is born at 36-37 weeks of gestation (late preterm), he’ll probably look like a small full-term baby.

As a baby’s gestational age decreases, her weight and size also decrease.

Extremely premature babies – for example, those born at 24 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, the cause is unknown. But 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 infection or 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 some other factors that are associated with a premature birth. These include poor or not enough nutrition, too much physical activity, smoking, alcohol and other drug use, too much stress, anxiety, depression, obesity, underweight and lack of prenatal care. Being under 17 years or over 35 years can also be a factor in premature birth. The best way to make sure your pregnancy goes well is to follow your doctor’s advice about:

• eating well
• not smoking, not drinking alcohol and not taking other drugs
• doing the right amount of physical activity (some, but not too much)
• managing stress,  depression and anxiety.

Even if you follow all the pregnancy advice, you might still have a premature baby. But if you look after your body, 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.

Premature labour: signs and symptoms

If you have any of the following symptoms, you should contact your health professional – that is, your midwife, doctor or hospital. These symptoms might or might not mean you’re in labour, but you should always have them checked out:

• a dull, low backache
• a feeling that your baby is pushing down or a feeling of pressure in your pelvis
• swelling in your hands, feet or face
• contractions that happen more than four times an hour
• nausea, vomiting or diarrhoea
• blurriness, double vision or other eye disturbances
• abdominal cramps, much like period pain
• your baby’s movements slowing down or stopping
• fluid or blood coming out of your vagina.

It might be that you just don’t feel right, even though you don’t have any particular symptoms. If this happens, trust your own instincts. See your doctor or go to the 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 normally and getting all he needs from your body, the longer he can stay in your womb, the better.

Premature babies: survival and development

More than 90% of premature babies survive. And survival rates keep getting better as medical knowledge gets better.

Survival is affected by how premature a baby is. For example, moderately preterm babies are more likely to survive than extremely preterm babies. Babies born after only 23 weeks have a reasonable chance of survival – more than 50%.

The majority of preterm children develop normally. 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 developmental problems. But even in extremely premature babies, severe developmental problems are still quite uncommon.