By definition, a premature birth is when a baby is born before 37 weeks of gestation. In humans, a normal gestational period is from 38-42 weeks. Another name for prematurity is pre-term birth or having a “premmie”.
Ideally, babies remain in the uterus until they are full term but for all sorts of reasons, this does not always happen. For every day and week that a baby is left to grow in the uterus, important size, growth and developmental changes occur. Not all of these are as obvious as others but they are no less important.
When a baby is born before they are due, they can have a range of health and developmental problems which need to be carefully managed. Though it’s important to remember that each and every baby is an individual and whilst two babies may be born at the same gestation, they may not share the same complications. Likewise, being born at full term is not in itself a guarantee that all will be fine; every pregnancy, mother and baby is unique.
The more premature a baby is, the more likely they are to have health and developmental concerns. This is why early surveillance and good ante-natal care and monitoring are so important for all mothers, but particularly those who fit into a high risk category.
Around 85% of premature births occur after 32 weeks of gestation. Currently in New Zealand, around 8% of all births are classified as being premature.
Often we do not know the cause. There is some research which suggests the rising rates of obesity both before and during pregnancy have contributed to the increase in prematurity numbers in later years. Assisted fertility technology has meant that there are more numbers of multiple births and older mothers conceiving. This combination has also added to the increase in premature births. Some mothers go into spontaneous labour and despite all medical attempts to stall or halt it, labour still progresses.
Some maternal health conditions make the uterine environment risky and it is safer for the baby to be born early than to remain in the uterus. In these cases, the health benefits for the baby versus the risks of being born early are carefully weighed up. There are also occasions when it is safer for the mother to have her baby earlier than when she is due.
Premature babies can be born either vaginally or by caesarian section. If the mother has had a spontaneous rupture of her membranes (her waters break) and there are no other complications, she may progress to deliver vaginally. But if there are concerns that vaginal delivery could be too traumatic and stressful for the baby because of their degree of prematurity, then a caesarian section delivery is often done.
This is a common condition in premature babies and is caused by the underdevelopment of their lungs. The more premature the baby, the more likely they are to experience Respiratory Distress Syndrome or RDS. A substance called surfactant is produced from around 28 weeks of gestation and for babies who are born before this time, breathing difficulties are more common. Surfactant helps to keep the tiny air sacs open in the baby’s lungs and without sufficient quantities; the airways cannot adequately exchange oxygen and carbon dioxide.
There are increased chances for baby’s that have had RDS to develop asthma in their early years.
It is standard practice for health professionals to “correct for age” when a child was born prematurely. For example, if a baby was born 10 weeks premature their corrected age would be 30 weeks. Until the child is two years of age, correcting for their weight, head circumference and length generally done. After this time, they are managed in the same way as their full term peers. Research has shown that by around the pre-school years, most premature babies have caught up with children of the same age in terms of their development. They may take longer and need more practice and support but eventually, most get to where they need to be.
Again, this depends on the weeks of prematurity and the baby’s birth weight. For a baby who is born at 24 weeks the chances of survival are around 58%, though by 28-30 weeks, these chances increase to 98% or more.
Specialist neonatal intensive care units are located within most large metropolitan maternity hospitals. Caring for premature babies requires highly specialised care, with medical and nursing expertise. Keeping the baby warm in a humidicrib is important and often, intravenous fluids and antibiotics are necessary.
When a baby is too young to breathe on their own, they need to have a tube inserted into their mouth or nose which goes down their trachea (wind pipe). A ventilator does the breathing for the baby by regularly pushes oxygen into their lungs. They may also be attached to heart and temperature monitors and have a drip inserted into their arm or through their umbilicus. Alarms are set so that staff are alerted to any change in the baby’s condition.
Some babies need to stay in special care or intensive care units for many weeks. If they have been very premature they may need to remain in hospital for many months.
With good care, chances are increased for premature babies to lead healthy and full lives. Early detection and management of developmental delay generally means the outcomes are much better for babies and their families.
All neonatal units have follow up programs and assessment processes in place. Depending on the extent of the prematurity, regular checkups occur throughout childhood. Teams which include pediatricians, neonatologists, nurses, physiotherapists, occupational and speech therapists and dieticians are all involved in the care of premature babies.