If i have had 3 pregnancies with gestation diabetes... what are my chances of developing full blown diabetes if i had a 4th pregnancy?

Unlikely: Gestational diabetes is a disorder of altered glucose metabolism. Your family history likely has diabetes which is a genetic defect. You are showing signs of that with pregnancy. It is likely after pregnancy as you get older you will develop dmll and will have to be treated for the rest of your life. It will be very important that you have close glucose monitoring with hba1c test for diag!

Pretty high...: Consider each pregnancy as a stress test for your pancreas; the more you have and the older you get without decreasing your weight and increasing your physical activity, the greater the risk for permanent diabetes mellitus.