Are pregnant women at a greater risk for developing diabetes?

Sort of... Pregnant women can develop gestational diabetes which can lead to complications for the mother and child, but generally disappears after the end of pregnancy.
Yes. The stress on the maternal system may cause hyperglycemia to be manifested just during pregnancy, then completely resolve after delivery. However, a high percentage of these patients will develop diabetes later in life, not because of the pregnancy, but because they were genetically predisposed.