Premature babies: What to expect from their development

• The early outlook
• Developmental milestones
• Immunisations
• Physical growth
• Very premature babies (below 26 weeks)

The early outlook
Babies born after week 33 often need only a relatively short time in the Neonatal unit, providing that they aren't suffering from an underlying condition (see below) and are progressing well. Babies born before week 33 will probably have a longer stay in the specialist baby unit and may need intensive care treatment for some time. Those born very prematurely are much smaller at birth, tend to be sicker and are more likely to have problems breathing and feeding in the early days, as well more likely to develop long-term problems.

Premature babies are at higher risk of:

• Breathing difficulties - because their lungs are immature. Babies may need to spend time on a respirator or be given addtional oxygen
• Hypothermia - because they don't have the necessary body fat to help regulate temperature, incubators guard against hypothermia by maintaining the tempertature constant for your baby
• Infection - because the immune system is less well developed
• Jaundice - because the liver is not fully developed
• Hypoglycaemia (low blood sugar) - because of feeding difficulties

And less commonly:

• Heart abnormalities
• Hearing and sight problems
• Internal bleeding

Developmental milestones
For at least the first year of his life, your baby is likely to develop more or less in line with his age as calculated from his due date, his corrected age, rather than his chronological age, as calculated from his birth date. So if your baby is three months old, but was born four weeks early, his corrected age is two months.

This is because your baby has missed out on development time in the womb and will need to make that up before developing as most babies do. You'll need to bear this in mind whenever you read any information about how babies develop month-on-month. Remember also that all babies develop differently and your baby's development may not reflect the development 'average' baby born at term. At the moment there are no charts showing the average development rate or weight gain or development particularly for premature babies against which to compare your baby's development.

It's also important to remember to consider your baby's prematurity when following advice about weaning and introducing cow's milk. The premature baby charity Bliss says that as a general rule, premature babies can be weaned between five and seven months (chronological age), but notes that the timing of introducing solids rests on your baby's individual progress and condition: You'll need to discuss the introduction of solids with your doctor to find what is best for your baby.

• Find out more about weaning a premature baby

When you take your baby for his routine developmental checks in the first three years, your doctor will take this difference between due and arrival dates into account. To foster healthy development and growth, she may prescribe vitamins and iron supplements for your baby, and will probably recommend a special formula for premature babies if you're not breastfeeding.

Most premature babies will have caught up with their peers developmentally by the time they are two years old, but some may take longer, particularly babies born over two months' premature. As he gets older, your child will be regularly assessed to check for some of the problems to which premature babies are more susceptible, such as hearing problems, impaired vision, learning difficulties, impeded development and growth. Doctors will also be alert to the less common occurrence of severe handicap. Regular assessment is important as many of the developmental difficulties of which premmies are at higher risk can be more successfully treated if detected early.

Immunisations
Because premature babies are at a higher risk of infection that term babies, the NHS recommends that immunisations for your baby follow the normal vaccination schedule for term babies, meaning he'll be due his first set of jabs at around 8 weeks (chronological age).

Physical growth
In the final three months in the womb a baby puts on body weight very quickly and continues to grow in length. Most premature babies won't have a problem catching up on this growth once they are born, but for very premature babies this may take longer: If a premature baby is born very small and then has feeding problems he may well fall off the growth charts for a time. This faster physical growth for premature babies is known as 'catch-up' growth and there are three phases of faster growth, first the head grows faster as the baby catches up on in-utero brain development, then baby puts on more weight and finally the faster growth is directed towards baby's length.

85% of premature babies complete this catch- up growth and are in-line with their age peers by the time they are two years old. Of the remaining children, available evidence suggests that most will catch up in their own time, and the majority of premature babies, even very tiny ones, will be of normal height in adulthood.

Very premature babies
Babies born at or before 25 weeks are at a higher risk of developing severe problems than babies born after this, but they do only form a tiny percentage of the total of premature births. According to the 2005 results of EPICure, the UK's first study following babies born this prematurely, 54% showed either mild or no difficulties at an average age of 6 years and four months. In detail, the study reported that:

• 20% had no problems
• 34% had relatively mild problems such as needing glasses, a squint or low/normal cognitive scores
• 22% had severe disability such as severe cerebral palsy (children not walking), very low cognitive scores, blindness or profound deafness
• 24% had moderate disability such as cerebral palsy (but walking), IQ/cognitive scores in the special needs range, or lesser degrees of visual or hearing impairment

Read more

• Best places to buy premature baby clothes

• Watch: A year in the life of a baby born at 25 weeks

• Look how strong Chris Hoy's premature son is now