How does gestational diabetes increase a baby's weight in the womb?

Glucose load: Normal fetal size and development depends in one way on receiving glucose from the placenta in a normal concentration.Baby begins to make its own Insulin supply in pregnancy, and the amount it makes is driven by the amount of sugar it encounters.With the excess from gd, the baby begins to store the excess anywhere it will go, both as fat and an increased organ size.

High sugar levels: High sugar levels from mom cross over to the baby, and the baby makes extra Insulin to lower its sugar levels. That Insulin makes baby grow bigger. That's why it's important for moms to control their blood sugars.