Premature birth

This section gives information on premature birth, potential risk factors and known causes and ways of lessening the risk. If you have, or someone you know has, suffered a premature birth, and would like additional support, please visit our In Memory section.

What is a premature birth?

A premature (or pre-term) birth is the birth of a baby before 37 completed weeks of pregnancy.

Babies are considered to be full term from the 38th week of pregnancy. At this point, they will have had enough time in the womb for their bodies to develop and function well, and they will have the best chance of healthy development.

How common is premature birth?

Despite improvements in antenatal and neonatal care, the number of premature babies born each year has not significantly decreased in the last 15 years.

Since the government started producing figures in 1994/5, the rate of premature births in the UK has stayed at around 7% of all births. That equates to about 45,000 premature births each year – or 125 every day.

Can we assess each woman’s risk of having a premature baby?

Research has identified some factors that may increase a woman's risk of having a pre-term birth.

The risk of experiencing a premature birth is slightly higher for women who are under 20 or over 35.

The risk is also higher if the pregnancy is a multiple pregnancy. The overstretching of the womb that occurs in a multiple pregnancy is thought to increase the risk of premature labour.

Smoking, using recreational drugs, having a high caffeine intake, having a poor diet, being underweight and undertaking over-strenuous physical activity can also all increase the risk of having a premature baby.

However, many women with no known risk factors can still have a pre-term baby.
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What are the causes of premature birth?

Much still remains to be learnt about why women go into pre-term labour. However, we do know that the causes of pre-term births can be structural or the result of pregnancy-related conditions, blood-related conditions or infections.

Let’s look at each of these possibilities in a bit more detail.

Structural
If there is not enough room in the womb for the baby to grow then premature birth may occur.

The baby may be weak and unable to thrive if, for instance, the placental blood supply is impaired. This too may lead to a premature birth.

If a woman has a weak cervix which dilates too soon this can lead to premature birth. If a woman is known to be at risk, for example, if she has had previous surgery which has damaged the opening to the womb, then a cervical stitch may help to prevent early dilation.

Pregnancy-related conditions
Certain medical conditions specific to pregnancy, if left untreated, can cause pre-term labour. Examples include pregnancy-induced diabetes and obstetric cholestasis (liver disease characterised by excessive itching).Treatment of pre-eclampsia sometimes requires an induced pre-term delivery.

Blood-related conditions
Some blood clotting disorders like Systemic Lupus Erythematosus (SLE) and Antiphospholipid Syndrome (APS) may increase the risk of premature birth. Renal disease also increases the risk. These disorders might be effectively treated with specific drug treatments under medical supervision.

Infections
Vaginal infections, such as gonorrhoea, chlamydia, trichomonas, bacterial vaginosis and group B streptococci have all been linked to pre-term labour. Bladder infections can also trigger early labour if left untreated.

Other factors
Possible links and risks discovered by researchers are often published. Some are more significant than others. Some research is only relevant to certain groups of people. But all research is welcome.

One study found that women with chronic gum disease in the second trimester of pregnancy were seven times more likely to go into pre-term labour.

Medical intervention
There are circumstances where premature delivery is initiated by medical staff. For instance, if a woman is suffering from pre-eclampsia or ante-partum haemorrhage and either the health of the mother or the baby is at risk, then premature delivery of the baby may be the only option. If the baby is not doing well in the womb this also may necessitate inducing a pre-term delivery.
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What happens if a woman has a premature baby?

Whilst the experience of a premature birth may be very stressful for all involved, there is seldom any adverse effect upon the mother's physical health. For the mother, physical recovery from premature labour and delivery should be no different than recovery from a later delivery.

Once pre-term labour is suspected most women will receive tocolytic drugs to stop the contractions. These drugs may stop labour altogether or delay it long enough for the mother to be given steroids and/or be transferred to a hospital with an available special care baby unit (SCBU) cot. Steroids help the baby’s immature lungs develop before delivery.

The effects on the baby of pre-term delivery depend on how many weeks the baby has been in the womb before delivery (gestational age).

Babies born closer to their due date and with a good birth weight will have a greater chance of survival than very small, very premature babies. Premature babies have less time in the womb to mature and develop. As a result they're often at increased risk of medical and developmental problems. However, neonatal care is making huge advances and there are many wonderful stories of tiny babies surviving despite the odds against them.
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