Why is this important?
Babies that are LGA are at a slightly increased risk of a complication called shoulder dystocia. This is when your baby’s head is born but their shoulder becomes stuck behind your pubic bone. This is an emergency, however, all our staff are trained to deal with this and undertake regular training on how to safely manage a shoulder dystocia.
How accurate are the scans?
We have estimated your baby’s weight using measurements taken on the scan which have been entered into a calculation formula. The accepted margin of error is around 10 to 15% which means your baby could be 10 to 15% larger or smaller than the estimated weight.
If your baby has been estimated to be LGA your Consultant Obstetrician will discuss your options with you. These may include Induction of Labour or Caesarean Birth. However as we cannot confirm your baby is LGA until after the birth, there is a chance these interventions will have been unnecessary.
How likely is this to occur?
Around half of shoulder dystocias occur in babies that are not LGA. However the chances of a shoulder dystocia can increase as the baby’s size increases.
For women without diabetes, the chances of shoulder dystocia are:
| Estimated weight of baby | Chance of shoulder dystocia |
| Under 4000g
(or 8lb 13oz) |
0.65% or
6.5 per 1000 babies |
| Between 4000 and 4500g
(8lb 13oz to 9lb 15oz) |
6.7% or
67 per 1000 babies |
| Over 4500g
(over 9lb 15oz) |
14.5% or
145 per 1000 babies |
What could having a shoulder dystocia mean for me and my baby?
90% of shoulder dystocia’s are resolved with some simple manoeuvres by staff, including changing your position and applying pressure to the area above your pubic bone. The remaining 10% of cases will require some more advanced manoeuvres to release the baby’s shoulder.
A very small number of babies will have short term and/or long term problems from a shoulder dystocia including:
- Short term weakness in the shoulder and arm
- Rarely long term damage to the nerves of the shoulder and arm
- Very rarely a baby may suffer a fracture to their collar bone or arm bone
In a severe case of shoulder dystocia it is possible that a baby may experience a brain injury from lack of oxygen.
What might Induction of Labour mean for me?
Opting for Induction of Labour (IOL) is a very individual choice and your Consultant will develop an Individualised plan of care based on your own circumstances. IOL for LGA alone has been shown to:
- Reduce the chance of shoulder dystocia from 67 per 1000 to 41 per 1000 babies
- Reduce the chance of an arm or collarbone fracture from 20 per 1000 to 4 per 1000
IOL for LGA has not been shown to make a difference to:
- Shoulder and arm nerve injuries
- APGAR scores
- Your chance of Caesarean birth
- Your chance of instrumental birth
- Rates of severe perineal tear
What happens now?
Following a discussion with your Consultant about the risks and benefits of the different options available to you, you can make a decision about which course of action you would like to take.
If you need more information to make a decision or have any more questions or concerns please ask your Maternity Team.