When a baby is born preterm, their weight can affect their chances of survival. Generally the heavier the baby for their gestational age, the better off they tend to be. Where the babies are a twin or triplet, often the smaller babies can experience more difficulties than their larger siblings (although this may not always be the case).
Babies less than:
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2,500 grams (or 5lb 9oz) are regarded as having a 'low birthweight'. This is the average weight for a baby at about 34 weeks gestation. |
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1,500 grams (or 3lb 5oz) are regarded as having a 'very low birthweight'. This is the average weight of a baby at about 29 weeks gestation. |
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1,000 grams (or 2lb 4oz) are regarded as 'extremely low birthweight'. This is the average weight of a baby at about 26 weeks gestation. |
In Australia in 1999, 5.2% of singleton babies, 50.1% of twins and 96.5% of triplets were classified as 'low birthweight'; 1.5% of all babies were 'very low birthweight' and 0.8% of babies were 'extremely low birthweight'.
Survival rates for babies less than 1000 grams (2lb 4oz) at birth is about 70%, but if they are 1,500 to 2,000 grams (3lb 5oz to 4lb 7oz) it can be as high as 95%.
If there are twins or more
Women having twins or more are at an increased risk of having their babies more preterm and lower in birthweight. The woman is also more likely to develop complications (such as
high blood pressure) or have her babies experiencing different growth patterns. All these factors can increase her chances of needing the labour to be induced or the babies born by Caesarean preterm.