Now that you're pregnant, it might seem that every part of your body is changing in some way. And you're probably right. However, one change you might not notice is a fluctuating blood sugar level.

Throughout your pregnancy, your body changes how it produces and uses insulin, a hormone that helps the sugar in the foods you eat enter your cells so it can be used as fuel.1

Normal changes in this process will make your blood sugar level go up and down, while still ensuring that your baby gets the right nutrition to grow properly. But a blood sugar level going too high or too low can cause problems for both of you.

Changes start early and continue throughout pregnancy

In the first trimester, your body uses insulin more effectively, so blood sugar (glucose) levels are lower than normal because both the placenta and the baby use glucose to grow.1

During the second and third trimesters, other important changes start to occur. Hormones produced by the placenta begin to cause insulin resistance, which means insulin isn’t as effective at getting sugar into your cells.1 

This makes your blood sugar level rise after a meal, and while that does provide your developing baby with a steady supply of fuel and nutrients, this change can sometimes cause an expecting mother to become diabetic – called gestational diabetes.2

How does diabetes affect pregnancy?

Diabetes is becoming more common in pregnancy.1 Up to 10 percent of U.S. women get diabetes during pregnancy.3-5 Although most women who get diabetes while pregnant have the gestational form, it is possible to develop other kinds of diabetes while you're pregnant.3,5 If diabetes is diagnosed during the first trimester of pregnancy, then it's probably type 2 diabetes.1

If a woman is at risk of developing diabetes, then she will usually have a gestational diabetes test during her first prenatal visit. Risk factors for gestational diabetes include:

  • Being overweight; i.e, a body mass index (BMI) of 25 (or 23 for Asian-Americans)1
  • Having a parent or sibling with diabetes1
  • Having gestational diabetes or insulin resistance in the past3
  • Experiencing an unexplained stillbirth or a birth defect in a previous pregnancy3
  • Having a previous birth of a large baby (9 pounds or more)3
  • Being a race other than Caucasian1
  • Having a health condition such as heart disease, high blood pressure, or high cholesterol1
  • Not being physical active1

Gestational diabetes is not usually diagnosed until the second or third trimester. If no diabetes risk factors are present, then an oral glucose tolerance test is given between the 24th and 28th week of pregnancy.1

For an oral glucose tolerance test, you drink a sugary liquid at the doctor's office and your blood sugar level is checked an hour later. If the resulting blood sugar level is 190 milligrams per deciliter (mg/dL) or higher, then you have gestational diabetes.1,3,5

If the results of this one-hour test are between 140 mg/dL and 190 mg/dL, then you will need to have a three-hour oral glucose tolerance test.

This test requires an overnight fast and then drinking the sugary liquid again at the doctor's office. Your blood sugar level will be checked when you arrive and then once every hour for three hours. If your blood sugar level is abnormal for two or more of these checks, you’ll be diagnosed with gestational diabetes.3

If you are diagnosed with gestational diabetes, then your obstetrician will likely recommend that you make changes to your diet.

So what can happen if you do have gestational diabetes? Possible problems include:3,5,6

  • Having a baby weighing more than nine pounds
  • Having difficulties in labor, such as a tear
  • Having a Cesarean delivery
  • Having high blood pressure
  • Having pre-eclampsia
  • Having liver problems
  • The baby having breathing troubles or low blood sugar
  • Stillbirth
  • Having a higher risk for type 2 diabetes later in life (and possibly the baby)

A woman with diabetes going into pregnancy faces similar risks. Plus, the risk of a birth defect is higher when blood sugar levels are not controlled in early pregnancy.1

Women with type 1 diabetes have a particularly high risk of dangerously low blood sugar levels (hypoglycemia) in early pregnancy. One reason is because the placenta and baby are using up some of your glucose. Another reason is that you will need to keep your blood sugar level under tighter control than normal to reduce the risk of a birth defect from high blood sugar.1

Importance of monitoring and managing blood sugar

If you have any type of diabetes, it's important to track your blood sugar level to make sure it's not too high or too low. Staying in a healthy range will help to prevent problems.

Women with gestational diabetes will be encouraged to check their blood sugar levels four times a day – once in the morning (fasting) and then two hours after each meal.3,5  If diet and exercise bring the blood sugar level close to normal, then you can probably cut back the testing to twice a day.3

But if lifestyle changes don't keep your diabetes in check, then you could need regular insulin injections.

Insulin is the first line of diabetes treatment in pregnancy because insulin does not cross the placenta.Because insulin resistance increases during the second and third trimesters, your dosage of insulin can fluctuate.

During labor and delivery, insulin resistance will decrease quickly. For a woman taking insulin, this change can lead to widely varying needs for insulin during labor and post-partum.1

If you do develop gestational diabetes, you’ll  need another oral glucose tolerance test 4-12 weeks after you give birth to determine if the diabetes has resolved.1 

A woman who has gestational diabetes has a much higher risk of developing type 2 diabetes, although lifestyle changes, including eating healthy and getting regular physical activity, can reduce this risk.

Because the risk of type 2 diabetes is higher if you had gestational diabetes, you will need to be screened for diabetes every 1-3 years.1,5

What you can do to reduce your risk of having blood sugar problems

There is much you can do to keep your blood sugar level from turning into a roller coaster. Lifestyle changes aren’t always easy, but the payoff is so worth it. For 80 percent of women with gestational diabetes, lifestyle changes will keep blood sugar levels close to normal.3

Maintain a healthy weight

Ideally, you’ll start your pregnancy at a healthy weight, which is a BMI of less than 25.7 If you are overweight when you become pregnant, be sure to consult with your health-care professional about how much weight gain is reasonable during your pregnancy.

Eat a healthy diet

Good nutrition can help prevent or control diabetes. Eating regular meals and snacks helps keep your blood sugar level steady. Three meals and 2-3 snacks are often recommended.6

Although there’s no "ideal" diet, recommendations for pregnant women include at least 2.5 ounces (70 grams) of protein daily, a minimum of six ounces (175 grams) of complex carbohydrates (from vegetables and fruits), and at least one ounce (28 grams) of fiber.1 Avoid simple carbohydrates like candy, sugary sodas, cookies, cakes, and baked goods. Working with your health-care professional or a registered dietician will help you figure out an optimal meal and snack plan.

Move more

Another key to preventing diabetes is regular physical activity, such as walking. The recommendations for pregnant women aren't any different from the standard advice for adults – get 30 minutes of moderate aerobic activity most days of the week; i.e., about 150 minutes weekly.6 It's also a good idea to reduce the amount of time you spend sitting still – get up and move around every 30 minutes or so.1

Know the warning signs of a high or low blood sugar level. Symptoms of a high blood sugar level include:8

  • Increased thirst
  • A need to urinate more frequently
  • Blurry vision

If your blood sugar level drops too low, then you might feel:1

  • Shaky
  • A fluttering heartbeat
  • Irritable
  • Confused
  • Sweaty
  • Hungry

Get regular prenatal checks

These checks can help you and your health-care professional find problems early. If you are taking insulin for gestational diabetes, then your health-care professional might recommend weekly testing starting at 32 weeks' gestation to keep closer track of your baby's health.5

Take a prenatal multi-vitamin/mineral supplement

Discuss with your health-care professional what kind of prenatal multi-vitamin/mineral supplement you need. It's possible that the mineral chromium will help support a healthy blood sugar level,9 so look for a prenatal supplement that contains chromium.

Having a low vitamin D level increases the risk of developing gestational diabetes, so be sure to test your vitamin D level. If the level is low, you might need a vitamin D supplement in addition to the amount in your prenatal supplement. Taking up to 4,000 International Units of vitamin D daily is likely safe during pregnancy.10,11


  1. Riddle M, ed. Standards of Medical Care in Diabetes – 2019. Diabetes Care 2019 Jan;41(Suppl 1):S1.
  2. Petraglia F, D'Antona D. Maternal adaptations to pregnancy: Endocrine and metabolic changes. [Accessed 3.22.19]
  3. AskMayoExpert. Gestational diabetes mellitus. Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2018.
  4. Gestational diabetes. U.S. Centers for Disease Control and Prevention. [Accessed 3.22.19]
  5. Caughey A, Turrentine M. ACOG Practice Bulletin – gestational diabetes mellitus. Obstet Gynecol 2018;131(2):e49.
  6. Gestational Diabetes. American College of Obstetrics and Gynecology. [Accessed 3.22.19]
  7. Stang J, Huffman L. Position of the Academy of Nutrition and Dietetics: Obesity, reproduction, and pregnancy outcomes. J Acad Nutr Diet 2016;116:677.
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  9. Chromium. Natural Medicines. [Accessed 3.22.19]
  10. Vitamin D. Natural Medicines. [Accessed 3.22.19]
  11. Zhang Y,Gong Y, Xue H, et al. Vitamin D and gestational diabetes mellitus: A systematic review based on data free of Hawthorne effect. BJOG 2018;125(7):784-793.