NY Times: Diabetes Is a Risk in Pregnancy That Car

[caryn]

Gestational diabetes, which affects about 4 percent of pregnant women, usually occurs midpregnancy, by the 28th week of gestation. Though its causes are unclear, there are some clues, namely placental hormones that suppress the action of insulin in the mother. This can result in insulin resistance: the mother's pancreas continues to spew out insulin but her body's cells fail to use it properly to process blood sugar, causing sugar levels to rise in the mother's blood.

This extra sugar, though not the mother's insulin, crosses the placenta and raises the baby's blood sugar level, giving the baby more energy...

http://www.nytimes.com/2008/10/28/health/28brod.html