To see exactly how it works, we need to look at glucose metabolism. A hormone (hPL) produced by placenta to causes changes that increase maternal blood glucose, this leaves more glucose circulating in mom's bloodstream, available to satisfy the glucose-greedy fetus. That's a good thing, but it doesn't come without a price.
To counteract those rising sugar levels as your pregnancy progresses, you secrete more insulin. So the placenta responds by pumping out even more hPL, which limits the effectiveness of that extra insulin. If your muscles and liver cannot easily use up all that sugar, you may end up with too much glucose in your blood. That's called insulin resistance, and in some moms (especially those who have additional risk factors), the vicious hPL-insulin cycle escalates into full-blown gestational diabetes.
As a response, a series of hormones produced by the uterus and mom's body - namely cortisol (the stress hormone), leptin (a hunger hormone) and adiponectin (an inflammation reducing hormone) - all flood mom's bloodstream, and further contribute to higher glucose. And this vicious cycle continues when there's too much glucose and insulin resistance during pregnancy.
Today, all pregnant women get screened for diabetes - even those at low risk (under 25, not obese, white, and no family history of diabetes). If you are diagnosed with gestational diabetes, your doctor will put you on a special diet, encourage you to exercise, and teach you how to monitor your blood sugar level, which you'll have to test several times a day.
Find out more about this book:YOU: Having a Baby: The Owner's Manual to a Happy and Healthy Pregnancy