Most babies who are born prematurely will stay in special care until around the time they were due to be born. The neonatal or special care baby unit, for a while, provides some of the basic functions that your womb would have. Because if this, you might feel confused about what to expect from your baby as he approaches his milestones.

Actual age and corrected age

You will often hear people in the health professions use the terms ‘actual age’ and ‘corrected age’ but what do they mean.

  • Actual age – this is the age of your baby according to the day he was born. For example, if he was born 8 weeks ago, he is 8 weeks old, even if he was born at 30 weeks gestation.
  • Corrected age – this takes into account the number of weeks your baby was born before term. For this calculation, term is classed as 37 weeks, so if your baby was born at 30 weeks gestation, he was born 7 weeks early. With that calculation when he is 10 weeks old, his corrected age is 3 weeks.

You may find that your baby’s corrected age is used for monitoring his weight gain and developmental milestones. For example, if your baby’s corrected age is 6 weeks, your health visitor might be expecting him to be reaching the milestones of a term baby who is 6 weeks old.

However, it is important to realise that not all babies are the same and even amongst term babies there can be big differences as to when babies reach their milestones. Bliss suggest you “look at your baby and consider the progress and development he or she has already made.”

Your baby’s future development

The majority of premature babies grow healthily and develop normally, although many factors need to be considered such as how premature they were and how low their birth weight was. Current statistics show that a baby born at 28 weeks has a 10 per cent chance of developing an ongoing problem while for a baby born at 32 weeks that risk is dramatically reduced to 1 in 50.

However, research into the long term effects of premature birth is still in the early stages. One of the largest studies of its kind, the Epicure study, has followed the development of surviving very premature babies, born at less than 26 weeks, up to school age. Its current findings show that at 30 months old;

  • 49 per cent had no disability
  • 24 per cent had a disability that was not severe
  • 24 per cent had a severe disability
  • 2 per cent did not survive

Another study has looked at how low birth weight affects a baby as he develops. It found that by the age of 8 years;

  • 11 out of 12 had caught up in size
  • Most children had caught up with their peers’ size by the age of 2 years
  • Children who were born with an appropriate weight for their gestational age were more likely to have caught up than those who were small-for-dates

Developmental problems

Most premature babies develop normally but some do have problems as they get older.

Sight – some tiny premature babies weighing less than 1000g (2lb 3oz) may develop a problem with their eyes known as retinopathy of prematurity (ROP). This is caused by high levels of oxygen stimulating the under-developed blood vessels in the eye to grow the wrong way. This causes scarring on the back of the eyes which impairs your baby’s vision. Most babies recover but 10 per cent need laser surgery to correct the problem which, if left
untreated, can cause blindness.

Hearing – small babies are more prone to hearing difficulties and most will have regular hearing tests starting immediately after birth to determine if there is a problem.

Cerebral palsy – unfortunately some premature babies develop cerebral palsy, which is particularly more likely in extremely tiny babies, under 1500g (2lb 15oz). More than 1 in 20 low birth weight babies will develop cerebral palsy.

Immunisations for your premature baby

Many parents of premature babies are unsure whether their baby should begin their immunisations at their actual age or their corrected age.

Premature babies are at an increased risk of infection than term babies because their immune systems are less mature, and they do not have as many antibodies passed on to them from their mothers.

The NHS Immunisation Advice line says, “Because a mother passes some protective antibodies to her baby across the placenta in the last three months of pregnancy, premature babies receive less of these antibodies.” Because of this, the Department of Health (DoH) recommends that all babies, regardless of their gestational age, receive their vaccinations at the same scheduled time. This means that your baby will receive his first course of immunisations when he is 8 weeks old (actual age).