Gestational diabetes (GD) is high blood sugar that develops during pregnancy. The extra blood sugar can cause your baby to gain weight—leading to a more difficult labor and delivery, higher risk for a cesarean section (C-section) and greater odds your baby may have trouble with breathing, jaundice, low blood sugar at birth and even injuries such as shoulder damage during delivery.
Women with GD are also more likely to develop dangerously high blood pressure, called pre-eclampsia, during pregnancy. And while GD clears up after birth, it leaves your child with a higher risk for obesity and type 2 diabetes and raises your own risk for heart disease and diabetes.
Researchers are learning more and more about GD’s causes, long-term effects, and prevention. Here’s what you should know about the “pregnancy diabetes” that affects up to 14% of women during pregnancy:
When researchers from Columbia University’s College of Physicians and Surgeons looked at health data for 125 million US pregnancies for a 2017 study in the journal BJOG: An International Journal of Obstetrics and Gynecology, they made a surprising discovery: Rates of gestational diabetes were 23 times higher in 2010 than in 1979.
Part of the difference could be that pregnant women were not always routinely screened for GDM in 1979 as they were by 2010. But the researchers say two big trends—the obesity epidemic and the rise of more pregnancies among women in their late 20s, 30s, and 40s—are responsible for the increase in “pregnancy diabetes.”
Overall, about 9% of pregnant women develop GD according to the Centers for Disease Control and Prevention.1 But rates vary wildly. Your odds may be higher if you have any of these risk factors:
Your baby’s need for water, oxygen, and nutrients including blood sugar grows and grows during pregnancy. To meet the demand, your body adjusts. The placenta—the organ that delivers nutrients and oxygen to your baby via the bloodstream—runs the show by releasing hormones that nurture the pregnancy.
Early in pregnancy, your blood sugar may actually drop as hormones increase your insulin levels and reduce the amount of blood sugar produced by your liver. But that changes as your pregnancy progresses. Hormones from the placenta including estrogen, cortisol and human placental lactogen go to work in your body, blocking insulin’s signals telling your cells to absorb blood sugar. Sugar (glucose) levels rise, feeding your baby.
As you reach the third trimester of pregnancy, your insulin sensitivity may be 50% lower than it was before you conceived!10 As your placenta grows, it pumps out more and more hormones. Your own body adjusts, burning more fat for fuel as your baby makes use of more and more blood sugar. And while your pancreas can usually make enough insulin to send the sugar you need into your own cells, that doesn’t happen for everyone. Your blood sugar may rise to levels considered risky for you and for your baby.
GD has virtually no symptoms. Some women may feel more thirsty than usual or need to urinate more often, but it can be difficult distinguishing between pregnancy-related changes and subtle signs of GD. So to diagnose GD, major medical organizations including the American College of Obstetricians and Gynecologists (ACOG) and the American Diabetes Association recommend that all pregnant women have a screening test for GD. (Since 50% of women with GD don’t have any risk factors according to ACOG, experts say it’s important to test everyone.)
Your test may be performed early in your pregnancy if you have any of the risk factors listed above. If not, you’ll have a blood sugar test between your 24th and 28th weeks of pregnancy. (If you had normal results on an early test, you should still be tested later in pregnancy, experts say.)
The test, called an oral glucose tolerance test, looks at how your body handles blood sugar. You visit your healthcare practitioner’s office or another test location and drink a beverage containing 50 grams of sugar. Your blood will be drawn and tested after an hour. A blood sugar reading of about 135 mg/dL or lower is considered normal. If your reading is higher, you will have a second, longer test. For this test, you must first fast for about 8-12 hours. You then sip a sugary drink containing 100 grams of dissolved sugar. Your blood will be tested before you have the drink, then after one, two and three hours.
Depending on the criteria your doctor uses, you are considered to have gestational diabetes if your fasting blood sugar is 95 to 105 mg/dL or higher, or if your blood sugar one, two or three hours after the test is 180-190, 155-165 or 140-145 respectively, according to ACOG.11
Untreated GD boosts your risk for pre-eclampsia—high blood pressure that can damage your organs and even be life-threatening for mothers— from 9% to 18%, according to ACOG. It nearly triples the odds that you’ll need a C-section for delivery. About 17 to 25% of women with GD have one, usually because their babies have high birth weights, compared to 9 percent of women without GD.
Since GD happens late in pregnancy, after your baby’s organs and body have formed, it doesn’t cause birth defects. But since it provides extra blood sugar while your baby is rapidly growing, it can lead to a high birth weight.12 This can make labor and delivery more difficult. It may also increase the risk for stillbirth. Since your baby’s pancreas is producing extra insulin to deal with the extra blood sugar, his or her blood sugar may drop to low levels after birth. Gestational diabetes also increases risk for premature birth and for problems for breathing problems and jaundice for a newborn.
Studies show that taking care of GD reduces these risks. It can cut odds for pre-eclampsia from 18% to 12% and reduce your baby’s risk for extra weight almost by half. Most women with GD can control their blood sugar with a specialized healthy diet plan and doctor-prescribed exercise, but some need insulin as well.
High blood sugar caused by GD returns to normal shortly after the placenta is delivered once your baby is born. But once you’ve had GD, you face serious, long-term health risks. Seventy percent of women with GD eventually develop type 2 diabetes.13 Your odds for heart disease are 20 to 50 percent higher than they are for women with normal blood sugar during pregnancy. 14 15
Your baby also faces higher lifetime odds for diabetes and obesity. But there’s hope. New research is finding new ways you can lower your risk for developing GD, for managing it for good health, and for cutting the risk of GD-related health problems later in life.