Gestational Diabetes And Pregnancy

When a woman becomes pregnant, the placenta produces hormones. These hormones may change the way insulin works. As a result, glucose levels in the bloodstream are too high, which can lead to gestational diabetes. If you are already a diabetic before pregnancy, your blood sugar may be harder to control while you are pregnant.

What Is Diabetes?

Diabetes is a condition that causes high levels of glucose (sugar) in the bloodstream. Your body uses glucose from food for energy. This energy is supplied to the body when insulin, a hormone, changes the glucose into energy. When your body does not make enough insulin, or your body doesn't use the insulin properly, the glucose levels in the bloodstream become too high, resulting in a condition called hyperglycemia.

For most women diagnosed with gestational diabetes, it goes away after the baby is born. You should have another glucose tolerance test six to 12 weeks after your baby is born to make sure that your glucose levels have returned to normal. Over half of the women who had gestational diabetes will develop diabetes within 20 years. Based on this risk, the American College of Obstetricians and Gynecologists (ACOG) recommends that women who were diagnosed with gestational diabetes be tested every three years for diabetes.1

Testing For, And Diagnosis Of, Gestational Diabetes

Screening for gestational diabetes is usually part of the routine prenatal care that you receive during pregnancy. It is important to tell your physician, or midwife, if you were diagnosed with gestational diabetes in a previous pregnancy. If this is your first pregnancy, or if the doctor or midwife has reason to believe that you might be at risk, you'll be tested. The test involves drinking a special sugary solution, then having blood drawn to test the glucose level in your blood. If the glucose level is higher than normal in the first test, a second test will be performed.

A diagnosis of gestational diabetes may be made when one or more of the following is observed:

  • A fasting blood glucose level is 92 mg/dL or higher
  • A 1-hour oral glucose tolerance test results in a blood glucose level of 180 mg/dL or higher
  • A 2-hour oral glucose tolerance test is 153 mg/dL or higher1

Risk Factors For Gestational Diabetes

A pregnant woman who is considered to be at average risk for developing gestational diabetes should undergo screening between the 24th and 28th week of pregnancy. This screening should involve either a two-step oral glucose challenge test or a one-step oral glucose challenge test. The one-step screening should be performed on all pregnant woman. The two-step screening should be performed if the blood glucose level in the one-step screening shows a glucose level of 180 mg/dL or higher.

A pregnant woman may be considered at high risk for developing gestational diabetes if she:

  • Has a strong family history of Type 2 diabetes
  • Is significantly overweight
  • Has been diagnosed with diabetes before pregnancy

Your physician or midwife should perform a risk assessment at your first prenatal visit.

Controlling Your Blood Sugar During Pregnancy

If your blood glucose levels are not well controlled during pregnancy, there is a greater risk of complications and birth injuries, including:

  • Delivering a very large baby (macrosomia). When the mother's blood sugar level is too high, the baby will receive too much sugar, causing the baby to be large. This can complicate your baby's delivery by increasing the risk of shoulder dystocia.
  • Increased amounts of amniotic fluid. There may be too much amniotic fluid surrounding the baby, a condition called polyhydramnios. This may cause the mother to develop preterm labor (before the 37th week of pregnancy).
  • Increased risk of birth defects. There is a higher risk for birth defects if the mother's blood sugar level isn't controlled, especially defects in the baby's spine, heart and kidneys. The baby is at a greater risk for having difficulty breathing at birth.
  • Pre-eclampsia/eclampsia in the mother. There is an increased risk of developing high blood pressure in pregnancy, called pre-eclampsia, causing problems for both the mother and baby. The mother may have to remain in the hospital where she and her baby can be closely monitored.
  • Urinary tract infections. The mother may develop a urinary tract infection that spreads from the bladder to her kidneys. Undiagnosed or untreated infections can also spread to the baby.

It is important that you check your blood sugar levels on a regular basis. Your physician may send you to see a diabetes educator where you will learn how to check your blood sugar with a glucose meter. Your physician will talk to you about how often you will need to check, and you will be asked to keep a record of the numbers.

It is extremely important that you follow a balanced diet during your pregnancy. Your physician or diabetes educator will go over your diet with you. You may also be encouraged to exercise. What type of exercise, and how much, is a decision that you and your physician will make together.

If your blood sugar levels are not well controlled by following a specific diet, it may be necessary for you to start on insulin injections. If you were a diabetic before you became pregnant and controlled your blood sugar by taking pills, you may need to switch to insulin injections during your pregnancy. Insulin does not cross the placenta; therefore, it does not affect the baby's blood sugar. Oral medications to control blood sugar during pregnancy (Glyburide and Metformin) are used, but they have not been approved by the Food and Drug Administration for use during pregnancy.1

If you need to take insulin injections, you will be taught how to safely do this. How much insulin and how often it is needed will often depend on your blood sugar readings. It is very important that your meals and insulin injections are correctly timed to avoid your blood sugar levels becoming dangerously high or low.

Monitoring Your Baby

If you are diagnosed with gestational diabetes, your physician may order specific testing throughout your pregnancy to monitor your baby's well-being. These tests may include ultrasounds and non-stress tests, and asking you to perform daily kick counts later in your pregnancy.

If you have been diagnosed with gestational diabetes, you may have specific tests done throughout your pregnancy. These tests include:

  • Hemoglobin A1C
  • Alpha-fetoprotein (AFP)

Depending upon how well your blood glucose levels were controlled during your pregnancy, and whether or not you required insulin to control your blood sugar, your baby may have low blood glucose levels after they are born. The newborn nursery staff will test the baby's blood sugar soon after their birth. If the blood sugar is too low, the nurses may feed the baby a small amount of formula, or you may be asked to breastfeed. This may raise the baby's blood sugar to a normal range. If feeding does not result in a rise in blood sugar, the baby may need a special IV fluid that contains glucose until their glucose levels stay within a normal range.

What To Expect In labor And Delivery

The decision as to how and when your baby will be delivered will be made between you and your physician. If your baby is expected to be large for their gestational age, or your blood sugar levels are not well controlled, it may be recommended that you deliver before your due date.

The American College of Obstetricians and Gynecologists recommend that delivery by cesarean section be considered when a baby's estimated weight (by ultrasound) is 4,500 grams (9 pounds, 9 ounces) or more. The greatest risk is developing a shoulder dystocia. Shoulder dystocia (difficulty delivering the shoulders after the baby's head is delivered) carries a high risk of oxygen deprivation and brachial plexus injuries. Babies of diabetic mothers often have more body weight and wider shoulders, which increases the risk of shoulder dystocia.

  1. Cunningham, F. (2014). Williams obstetrics (24th ed.). New York, NY: McGraw-Hill.