Gestational Diabetes: Sorting the Evidence From the Noise

Key takeaways

• Usual screening time: 24 to 28 weeks of pregnancy
• ADA glucose targets in pregnancy: fasting under 95 mg/dL; under 140 mg/dL one hour or under 120 mg/dL two hours after meals, unless your team sets others
• Most useful single change: Follow the eating plan your care team or a registered dietitian gives you, spreading carbohydrates through the day.
• Commonest mistake: Skipping meals to keep numbers down, which can cause low blood sugar.
• See a doctor if any of the signs under "When to speak to a doctor" below apply to you.

What it is

High blood sugar that develops during pregnancy in someone who did not have diabetes before. It sits within Pregnancy. The figures come from the bodies named at the foot of this page.

The numbers, in one place

What helps

What follows is the practical part: the things guidance actually asks of you.

• Follow the eating plan your care team or a registered dietitian gives you, spreading carbohydrates through the day
• Check your blood sugar as often as you are asked and bring your log to visits
• Walk or stay active most days if your provider agrees; activity after meals can help lower blood sugar
• Take insulin or other medicines exactly as prescribed if diet and activity are not enough
• Keep your postpartum glucose test appointment and tell future doctors you had gestational diabetes

What to avoid

What to steer clear of, and why it catches people out.

• Skipping meals to keep numbers down, which can cause low blood sugar
• Sugary drinks and juice, which raise blood sugar quickly
• Assuming the risk is over once the baby is born

In depth

In the second half of pregnancy, the placenta releases hormones that make the body less responsive to insulin. This is normal and helps keep more glucose available for the baby. Most people make extra insulin to compensate. Gestational diabetes develops when the pancreas cannot keep up with this extra demand, and blood sugar rises above the target range.

Glucose crosses the placenta easily, but insulin does not. When the parent's blood sugar is high, the baby receives extra glucose and makes more insulin of its own, which acts like a growth hormone. This is why gestational diabetes can lead to a large baby, a harder birth, and low blood sugar in the newborn shortly after delivery, when the extra supply suddenly stops.

For most people, blood sugar returns to normal soon after birth because the placenta is gone. But the diagnosis reveals that the body was already under strain, and the risk of type 2 diabetes in later years is much higher. Gestational diabetes is best seen as an early warning that gives you time to act, not just a pregnancy problem that ends at delivery.

Signs and symptoms

• Usually no symptoms at all, which is why everyone is screened
• Increased thirst or needing to urinate more than usual, though both are common in pregnancy anyway
• Tiredness beyond the usual tiredness of pregnancy
• A baby measuring larger than expected or extra amniotic fluid on ultrasound
• Sugar found in a routine urine check

Causes and risk factors

• Placental hormones that increase insulin resistance in later pregnancy
• Overweight or obesity before pregnancy
• Gestational diabetes in a previous pregnancy or a previous large baby
• A family history of type 2 diabetes
• Polycystic ovary syndrome (PCOS) or prediabetes
• Being of African American, Hispanic or Latino, American Indian, Alaska Native, Asian American or Pacific Islander descent, groups with higher rates

How it is checked

Most US practices use a two-step approach. First comes a glucose challenge test: you drink a sugary solution and have blood drawn an hour later, without needing to fast. If the result is above a cutoff, you return for a longer fasting test with several blood draws over a few hours. Some practices use a single fasting two-hour test instead.

People with risk factors are often tested earlier in pregnancy, sometimes at the first visit, to look for diabetes that was present but undiagnosed before pregnancy. An HbA1c test may be used at that early stage. After diagnosis, home blood sugar checks, usually fasting and after meals, show how well the eating plan and activity are working.

Treatment and support options

Medical nutrition therapy

The core of treatment is an eating plan that spreads carbohydrates across three meals and several snacks, pairs them with protein and fat, and favors high-fiber choices that raise blood sugar more slowly. A registered dietitian can build a plan around foods you enjoy and your culture. Many people find their numbers improve within a week or two of changes.

Physical activity

Muscles use glucose when they work, and activity makes the body more sensitive to insulin. A short walk after meals can noticeably lower after-meal readings. Unless your provider says otherwise, aim for regular moderate activity most days. Check with your provider if you have any pregnancy complication that limits exercise.

Insulin

If targets are not met with food and activity, insulin is the preferred medicine in pregnancy because it does not cross the placenta in meaningful amounts. Needing insulin is not a failure; it reflects the hormones of pregnancy. Your team will teach you how to inject, adjust doses, and recognize and treat low blood sugar.

Oral medicines

In some situations, your doctor may discuss oral medicines such as metformin. These do cross the placenta, and guidelines generally favor insulin first, so the choice depends on your circumstances and preferences. Ask about the benefits and trade-offs for you.

Monitoring the baby

Depending on how well blood sugar is controlled and whether medicine is needed, your team may add growth ultrasounds and tests of the baby's well-being in late pregnancy. They will also discuss the timing of birth, which may be earlier than your due date if diabetes is harder to control.

Prevention

• Reach a healthier weight before pregnancy if you are able
• Stay physically active before and during pregnancy
• Ask for early testing if you have risk factors
• Breastfeed if you can, which is linked to a lower risk of type 2 diabetes later
• Keep up diabetes screening for life after a pregnancy with gestational diabetes

Day to day

The first weeks after diagnosis can feel overwhelming: finger-sticks several times a day, new food rules and frequent appointments. Most people settle into a routine. Keep your meter, snacks and log together, note what you ate when a reading is high, and bring patterns to your dietitian rather than blaming yourself for a single number.

After birth, blood sugar usually returns to normal and you can stop checking unless told otherwise. The work then shifts to the long term: the postpartum glucose test, regular screening afterward, and habits that lower diabetes risk. Let every future doctor know about your history, and get tested early in any future pregnancy.

For specific groups

Future pregnancies

Having gestational diabetes once makes it more likely to happen again. Ask for early testing in the next pregnancy, and use the time between pregnancies to work on weight and activity if relevant, which can lower that risk.

The baby

Babies born after gestational diabetes may have their blood sugar checked in the first hours after birth. Early, frequent feeding helps. Later in life, these children may have a higher risk of obesity and type 2 diabetes, so healthy family habits matter.

People with PCOS

PCOS involves insulin resistance, which raises the chance of gestational diabetes. Your provider may suggest testing earlier in pregnancy and closer attention to blood sugar throughout.

Questions to ask your doctor

• What are my blood sugar targets, and when should I check?
• Can I see a dietitian, and is it covered by my insurance?
• What should I do if my readings are high several times in a row?
• Will I need extra ultrasounds or tests for the baby?
• How will gestational diabetes affect the timing and plan for birth?
• When and how should I be tested after the baby is born?

More questions, answered

Did I cause gestational diabetes by eating sugar?

No. Gestational diabetes is driven by pregnancy hormones and how your body responds to insulin, influenced by genetics and other factors. Diet is a powerful tool for managing it, but eating sweets before diagnosis did not cause it.

Do I have to cut out carbohydrates?

No. You and your baby need carbohydrates. The aim is the right amount at each meal, spread through the day, and choosing slower-digesting sources. Very low-carbohydrate diets are not recommended in pregnancy without guidance.

Will my baby have diabetes?

Babies are not born with diabetes because of gestational diabetes. They may have low blood sugar briefly after birth and may have a higher risk of obesity and type 2 diabetes later in life, which healthy habits can help reduce.

Can I still have a vaginal birth?

Many people with gestational diabetes have vaginal births. The chance of cesarean birth is higher if the baby is very large. Your team will discuss timing and the best approach based on your blood sugar control and the baby's growth.

Is breastfeeding still possible?

Yes, and it is encouraged. Feeding soon after birth helps stabilize the baby's blood sugar, and breastfeeding is linked to a lower risk of type 2 diabetes for the parent. Some people choose to express colostrum in late pregnancy; ask your team whether this is appropriate for you.

Why is the urine test not enough to diagnose it?

Sugar can appear in urine during normal pregnancy because the kidneys handle glucose differently, and it may be absent even when blood sugar is high. Blood tests are needed for an accurate diagnosis.

Related topics

• Type 2 Diabetes: Sorting the Evidence From the Noise (Diabetes)
• What the Guidance Really Says About Vaccination in Pregnancy (Vaccinations)
• Listeria in Pregnancy: What Published Guidance Supports (Food Safety)
• What the Guidance Really Says About Diabetes and the Kidneys (Kidney Health)

Where to go next

• Gestational Diabetes, Explained Without the Jargon
• A Working Checklist for Gestational Diabetes
• Gestational Diabetes — the reference entry
• Pregnancy and Postpartum: The Complete Guide
• What the Guidance Really Says About Preeclampsia Warning Signs
• Vaccines During Pregnancy: What the Evidence Actually Says

When to speak to a doctor

Call your care team if your readings stay above your targets, or if you are very thirsty, urinating much more than usual or feel shaky and sweaty. Call 911 if you become confused, cannot stay awake, have a seizure or are unable to treat a low blood sugar.

Where this comes from

• CDC — Gestational Diabetes
• American Diabetes Association — Standards of Care in Diabetes
• National Institute of Diabetes and Digestive and Kidney Diseases — Gestational Diabetes

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.