why are infants of longstanding diabetic mothers microsomic/have IGUR?

[akilysa]

I have seen this a lot and it confuses me. I understand why infants of type II diabetic mothers / mothers w/ gestational diabetes are macrosomic. It makes sense to me that these mothers have chronic hyperglycemia, the fetus grows bigger, and then when baby is born, baby is at risk for hypoglycemia b/c baby is used to putting out a huge amount of insulin all the time.

But I don't understand why longstanding diabetics (like type I) have microsomic babies. It seems like these babies should also be macrosomic since these moms presumably also have chronic hyperglycemia. The main difference I can come up with is that these moms may not be producing any insulin at all, whereas gestational/type II may be hyperinsulinemic and just have high insulin resistance. Can anyone help explain?

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[thehundredthone]

This happens uncommonly, and is due to placental insufficiency as a microvascular complication of diabetes. Also 15% of babies born to type II DM mothers can be SGA.

http://www.gestation.net/PDFs/IUGR new concepts - AJOG Review.pdf

 

[Phloston]

I've read about this too. We hear frequently about the whole macrosoma/shoulder dystocia scenario secondary to maternal diabetes, but the latter is a risk factor for IUGR as well. I've never delved into the mechanism, but I'd assume thehundredthone is probably right. Diabetes in general = microvascular complications.