Hi Dr. O'Leary. I honestly believe it is more important what kind of shape your body is in than your absolute age. Some people in their 20's have multiple severe medical problems and many women in their 30s, 40s and 50s are in excellent health. There are concerns with older women of an increased risk for genetic problems in offspring as well as increased problems with pregnancy such as premature labor, pre-eclampsia, etc. The main concern with gestational diabetes is growing a fat baby.
Fat babies have two main potential problems.
One major problem can be a shoulder dystocia, which is the shoulder getting caught behind the women's pubic bone after the head is delivered. This occurs more often in diabetic women who have large babies. The other problem is in the nursery once the umbilical cord is cut, the babies high sugar supply is cut off and frequently their insulin levels remain high for several days causing their sugars to bottom out. Consequently they often need extra sugar with their milk or through an IV and have their sugars weaned down slowly over several days. I will be 40 in four months when my fourth child is born.