Because carbohydrates raise blood glucose, particularly in those with diabetes, reducing carbohydrate consumption can often improve glucose control during pregnancy. Yet low-carb and ketogenic diets remain controversial in this setting, largely due to concerns about ketosis and fetal development.
This article explores what gestational diabetes is, how carbohydrate reduction may help, and what current evidence suggests about the safety and potential role of low-carb and ketogenic approaches during pregnancy.
What Is Gestational Diabetes?
Gestational diabetes is a form of diabetes that develops during pregnancy, usually in the second or third trimester. During this time, placental hormones naturally increase insulin resistance in order to direct nutrients toward the growing fetus. Although this is a normal physiologic adaptation of pregnancy, some individuals cannot produce enough additional insulin to fully compensate for the increased insulin resistance, causing blood glucose levels to rise.
Several factors can increase the risk of gestational diabetes, including:
- Insulin resistance or prediabetes
- Overweight or obesity
- Prior gestational diabetes
- PCOS/PMOS
- Family history of type 2 diabetes
- Advanced maternal age
- Certain racial and ethnic backgrounds, including Pacific Islanders, Native Americans, Hispanics, and African Americans
How Is Gestational Diabetes Diagnosed?
Gestational diabetes is typically diagnosed between 24 and 28 weeks of pregnancy using a 75-gram oral glucose tolerance test (OGTT). This test involves drinking a beverage containing 75 grams of glucose after an overnight fast and measuring blood glucose levels over the next two hours. According to widely used international criteria, gestational diabetes is diagnosed when one or more of the following blood glucose values are met or exceeded:
- Fasting glucose: ≥92 mg/dL (5.1 mmol/L)
- 1-hour glucose: ≥180 mg/dL (10.0 mmol/L)
- 2-hour glucose: ≥153 mg/dL (8.5 mmol/L)
Consuming at least 150 grams of carbohydrate daily for the three days before testing – and at least 50 grams in the final meal before the overnight fast – is commonly recommended to help ensure accurate results.
Women who prefer not to increase carbohydrate intake before an OGTT should discuss alternative screening options with their healthcare provider. Depending on the clinical situation, alternatives such as fasting glucose, HbA1c, continuous glucose monitoring, or home blood glucose monitoring may be considered, although these approaches may not detect all cases of gestational diabetes.
Why Blood Sugar Control During Pregnancy Matters
Maternal glucose crosses the placenta easily. When blood glucose levels remain elevated, the fetus produces more insulin in response to the excess glucose, which can promote excessive growth and fat storage.
Poorly controlled gestational diabetes increases the risk of macrosomia (large-for-gestational-age infants), neonatal hypoglycemia, and preterm birth, along with obesity, insulin resistance, and type 2 diabetes later in life. Because of these risks, minimizing glucose excursions – especially after meals – is one of the primary goals of treatment.
Gestational diabetes usually resolves after delivery as pregnancy-related insulin resistance declines. However, women who develop GDM remain at substantially increased risk for type 2 diabetes and other cardiometabolic conditions later in life.
Blood Glucose Targets for Gestational Diabetes
Once gestational diabetes is diagnosed, the primary goal is maintaining blood glucose levels within target ranges, particularly after meals, to support healthy pregnancy outcomes.
Although targets may vary slightly among healthcare providers, the ADA currently recommends the following glucose goals for many women with gestational diabetes:
- Fasting glucose: less than 95 mg/dL (5.3 mmol/L)
and either - 1 hour after meals: less than 140 mg/dL (7.8 mmol/L) OR
- 2 hours after meals: less than 120 mg/dL (6.7 mmol/L)
Many women can achieve these targets through nutrition and lifestyle changes alone, while others may require medication or insulin.
Regular glucose monitoring helps determine whether treatment goals are being met and whether adjustments are needed.
Why Lower-Carb Diets Often Improve Gestational Diabetes
The Dietary Reference Intakes (DRIs) published in 2006 set a recommended carbohydrate intake of 175 grams per day during pregnancy, a target several organizations, including the American Diabetes Association, continue to endorse. Importantly, this recommendation was derived from estimates of the glucose needed by the mother’s brain and the developing fetus, with an additional margin added for pregnancy, rather than from clinical trials evaluating different carbohydrate intakes during pregnancy.
Because carbohydrates raise blood glucose more than protein or fat, reducing carbohydrate intake can effectively lower blood glucose levels. In women with gestational diabetes, studies suggest this approach may provide several benefits, including:
- Reduced post-meal blood glucose levels
- Modest improvements in fasting glucose in some studies
- Achievement of glycemic targets through dietary therapy
- Reduced maternal hyperglycemia, which may decrease fetal exposure to excess glucose
- Potential reductions in excessive fetal growth and macrosomia
Most studies have evaluated moderately carbohydrate-restricted diets rather than ketogenic diets, and many have reported improvements in glucose control, although findings have been mixed.
Ketosis During Pregnancy: Normal Physiology, Not Automatically Dangerous
Many people are surprised to learn that ketosis during pregnancy is not automatically harmful.
Ketone production is a normal physiologic feature of pregnancy, particularly during fasting and in the later stages. Pregnant women naturally enter ketosis more rapidly during fasting than nonpregnant individuals due to increased energy demands and changes in maternal metabolism.
Further supporting the role of ketones in normal pregnancy, a 2022 study found substantial BHB concentrations in placental tissue and umbilical cord blood throughout gestation. Placental BHB concentrations were approximately 1–3 mmol/L throughout gestation, while cord blood concentrations ranged from roughly 0.3–3.1 mmol/L. The authors concluded that ketones appear to serve as physiologic energy substrates that may support fetal growth and development.
More recently, a 2026 review noted that ketones can cross the placenta and may contribute not only to fetal energy metabolism but also to lipid and cholesterol synthesis needed for growth and development.
This does not prove that ketogenic diets are universally appropriate during pregnancy. However, it does challenge the common belief that nutritional ketosis is inherently abnormal or incompatible with healthy fetal development.
Nutritional Ketosis Is Not the Same as Ketoacidosis
Much of the concern about ketosis during pregnancy stems from confusion between nutritional ketosis and diabetic ketoacidosis (DKA), which are very different metabolic states.
DKA occurs when insulin levels become critically low, causing the body to produce excessive ketones while blood glucose rises to dangerously high levels.
Nutritional Ketosis
- Mild to moderate blood ketone (beta-hydroxybutyrate, or BHB) levels (0.5-3.0 mmol/L)
- Normal blood glucose levels
- Adequate insulin present
- Normal blood pH
Diabetic Ketoacidosis
- Very high ketones (typically BHB >10 mmol/L)
- Very high blood glucose levels (typically >250 mg/dL/14 mmol/L)
- Severe insulin deficiency
- Acidic blood pH
- Nausea, vomiting, weakness, and other signs of illness
- Requires immediate medical evaluation and treatment
Recognizing this distinction is important when evaluating the potential risks and benefits of low-carbohydrate and ketogenic diets during pregnancy.
Could a Well-Formulated Ketogenic Diet Help Some Women With GDM?
Anecdotal reports from clinicians and patients suggest that some women with gestational diabetes may achieve substantial improvements in glucose control with very-low-carbohydrate or ketogenic diets under medical supervision. Potential benefits may include smaller glucose excursions, lower insulin requirements, reduced medication needs, and improved satiety.
However, ketogenic diets may not be a good fit for every pregnant woman. Some may experience nausea, food aversions, reduced appetite, or difficulty meeting their nutritional needs while consuming very few carbohydrates during pregnancy. In these cases, a less restrictive low-carb approach that maintains blood glucose within target ranges may be more comfortable, sustainable, and appropriate.
Importantly, clinical trials evaluating ketogenic and very-low-carbohydrate diets during pregnancy remain limited. Therefore, individualized care and close monitoring are essential.
Important Safety Considerations
A well-formulated ketogenic or low-carb diet during pregnancy requires careful monitoring, appropriate medical supervision, and attention to nutrient needs.
Glucose and Ketone Monitoring
Monitoring can help distinguish appropriate nutritional ketosis from potentially concerning metabolic states and ensure that blood glucose remains within target ranges.
Depending on the individual situation, monitoring may include BHB, fasting glucose, and post-meal glucose levels. Your healthcare provider can help determine an appropriate testing schedule for glucose and ketone monitoring based on your individual needs and treatment goals.
Medical Supervision
Women with gestational diabetes — especially those taking insulin or other glucose-lowering medications — should work closely with qualified healthcare professionals when implementing lower-carb or ketogenic approaches during pregnancy.
Adequate Nutrition and Energy Intake
A well-formulated ketogenic or low-carb diet during pregnancy should focus on nutrient density, sufficient protein, and adequate energy intake to support both maternal and fetal health. Prioritizing protein intake is especially important during pregnancy to support fetal growth and development. In addition, particular attention should be paid to key pregnancy nutrients such as folate, choline, iodine, iron, calcium, and DHA. Pregnancy is not the time to diet or restrict calories.
The good news is that many nutrient-dense, lower-carb foods can support stable glucose levels during pregnancy while providing important nutrients for both mother and baby.
Protein Foods
- Eggs
- Meat and poultry
- Fully cooked low-mercury seafood, such as salmon, sardines, herring, freshwater trout, cod, flounder, sole, shrimp, and scallops
- Greek yogurt, cottage cheese, and cheese made from pasteurized milk
- Tofu and tempeh
Healthy Fats
- Avocados
- Butter
- Cream
- Olive oil
- Nuts and nut butters
- Seeds
Low-Carb Vegetables
- Asparagus
- Bell peppers
- Broccoli
- Brussels sprouts
- Cauliflower
- Leafy greens
- Zucchini
- Other vegetables on this list
Slightly Higher-Carbohydrate Foods
Depending on your blood glucose levels, you may be able to eat:
- Berries
- Small portions of other fruits
- Small amounts of potatoes, sweet potatoes, or legumes
Because glucose responses vary considerably, personalization matters more than rigid carbohydrate targets. This includes monitoring how you feel along with your blood glucose and ketone levels.
For more information about nutritional management of gestational diabetes with a lower-carb approach, read Real Food for Gestational Diabetes: An Effective Alternative to the Conventional Nutrition Approach, by Lily Nichols, RDN, CDE.
Key Takeaways
A diagnosis of gestational diabetes can feel overwhelming, but it can often be managed successfully with dietary changes.
Current pregnancy guidelines recommend a minimum carbohydrate intake of 175 grams per day. However, emerging evidence suggests that women with gestational diabetes may benefit from lower-carbohydrate approaches.
Ketone production is a normal part of pregnancy physiology, and current evidence does not support the belief that nutritional ketosis, unlike diabetic ketoacidosis, is harmful during pregnancy.
Ultimately, no one-size-fits-all approach exists. The goal is to support healthy blood glucose levels while providing adequate nutrition for both mother and baby.
