Type 1 or 2 diabetes and macrosomia

Macrosomia is a difficulty associated with diabetes – in which the baby is large for their gestational age, often weighing more than 4.5kg at birth.

This is caused by the mother’s high blood glucose levels transferring across to the baby. The baby then produces more insulin to deal with the high blood glucose levels, which can make them grow larger than normal - especially around the shoulder, chest and abdomen.

The likelihood of this is fairly high – almost half of pregnancies for women with Type 1 diabetes and almost a quarter of those with Type 2 result in babies that are large for gestational age.

This can affect labour and birth in women who have diabetes, increasing the risk of shoulder dystocia – in which there is difficulty delivering the baby’s shoulders after the head has been born. This requires some additional manoeuvres at birth to help the baby out. Your midwife can explain these to you.

If there is delay at this point of labour, your baby may not be able to breathe. Because of this risk, you are more likely to have an assisted birth, induction or caesarean to get the baby out safely. In most cases of shoulder dystocia the baby is born promptly and safely.

Read more: Royal College of Obstetricians and Gynaecologists: shoulder dystocia: (PDF, 223kb)

If your baby has been producing extra insulin, then their blood glucose levels can drop too low soon after birth. Because of this, they need to be fed within 30 minutes after birth and at regular intervals, and their blood glucose levels will need to be monitored. Additional treatments such as tube feeding or IV dextrose treatment may be needed, and they may need to be cared for in a specialist baby unit in the hospital.


  1. NHS Choices. Gestational diabetes – complications,http://www.nhs.uk/Conditions/gestational-diabetes/Pages/Complications.aspx
  2. RCOG (2013) Shoulder dystocia: information for you, Royal college of obstetricians and gynaecologists, https://www.rcog.org.uk/globalassets/documents/patients/patient-informat...
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Read more about the effects of diabetes and pregnancy

More sections on type 1 or 2 diabetes in pregnancy

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