Diabetic mothers have bigger babies due to blood flow in pregnancy

by Barbara Hewitt on December 13, 2016

Scientists have discovered why mother with diabetes have bigger babies after studying how the blood flows from the mother to the unborn child.

They found that blood flows preferentially to the placenta instead of the brain in foetuses of mothers with diabetes, hence increasing the size of the infant.

New Born BabyLead author of the study Aparna Kulkarni, a paediatric cardiologist from the Bronx-Lebanon Hospital Centre in New York, said it is well documented that maternal diabetes affects the foetal organs and his team wanted to find out more.

‘Babies born to mothers with diabetes are sometimes bigger, especially if the diabetes is uncontrolled, and the placenta is larger. There is data to suggest that some other organs such as the pancreas and the kidneys in the foetus might be affected,’ she explained.

Dr Kulkarni’s previous research identified subclinical changes in the heart muscle of foetuses of mothers with diabetes. In the current study she investigated whether these foetuses had changes in blood circulation.

This study included 14 foetuses of mothers with type 1 or 2 diabetes and 16 foetuses of mothers without diabetes as a control group. Nine of the diabetic mothers used insulin, three took oral medications, and two used diet alone to control their glucose levels.

The research found that, compared to foetuses in the control group, in foetuses of diabetic mothers more blood flowed to the placenta and was diverted away from the brain.

Specifically, foetuses of diabetic mothers had lower placental resistance and compliance, lower blood flow to the arteries in the brain, a reduced proportion of blood flow to the brain than the placenta and a lower cardiac output.

‘The computational model equivalent of the foetal circulation is an electrical circuit where there are resistances and compliances. It is easier for blood to flow to the placenta, and harder for blood to flow to the brain,’ said Kulkarni.

She explained that the placenta in foetuses of diabetic mothers have changes in their blood vessels and are known to be large, therefore likely receive more blood supply. But she added that the lower proportion of blood supplying the brain is an interesting finding and could have bigger implications.

‘The placenta gets taken away after a baby is born so it’s no longer a part of the circulation. But it’s possible that the reduced circulation to the brain in utero could affect the baby through life,’ she pointed out.

‘We don’t know enough about why this redistribution of blood flow occurs or the implications it might have. More research is needed to find out if this has any long-term impact on the health of the baby and whether anything can be done to prevent it,’ she added.

‘At the present time, I don’t think any changes should be made in management of pregnant women with diabetes based on these findings. Standard obstetric recommendations for strict glucose control and healthy lifestyle should be continued,’ she concluded.


The opinions expressed in this article do not necessarily reflect the views of the DiabetesForum.com Community and should not be interpreted as medical advice. Please see your doctor before making any changes to your diabetes management plan.

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