Hi

This is purely speculation but they may want to check for your HBA1C levels.
My DH is Diabetic so I can tell you a bit about it, before I do may I add that it doesn't mean you are Diabetic if you get raised levels during pregnancy, although it may feel like little comfort you can get Gestational Diabetes, meaning that although you have never previously been dianosed with Diabetes, you can get it for the duration of your pregnancy.
My DH has to have fasting blood tests a couple of times a year to test his HBA1C, to see how well his Diabetes is under control. He usually has to fast from 10pm ish until the test takes place mid morning the next day.
I'm guessing if this is necessary for you they will want to do it whilst keeping a closer eye on you.
HBA1C levels/test.
Enlarge Haemoglobin, in your blood, joins up with glucose to form the chemical called HbA1c In the blood stream are the red blood cells, which are made of a molecule, haemoglobin. Glucose sticks to the haemoglobin to make a 'glycosylated haemoglobin' molecule, called haemoglobin A1C or HbA1C. The more glucose in the blood, the more haemoglobin A1C or HbA1C will be present in the blood.
Red cells live for 8 -12 weeks before they are replaced. By measuring the HbA1C it can tell you how high your blood glucose has been on average over the last 8-12 weeks. A normal non-diabetic HbA1C is 3.5-5.5%. In diabetes about 6.5% is good.
The HbA1C test is currently one of the best ways to check diabetes is under control; it is the blood test that gets sent to the laboratory, and it is done on the spot in some hospital clinics. Remember, the HbA1C is not the same as the glucose level.
I hope this helps

Good luck
