Managing gestational diabetes: How nutrition can support a healthy pregnancy

Core Nutrition Dietitians

Aug 28

5 min read

Gestational Diabetes Mellitus (GDM) occurs when hyperglycemia (high blood glucose levels) develops during pregnancy, most often in the second or third trimester. It occurs when the body becomes more resistant to insulin—a normal physiological change in pregnancy—but the pancreas cannot produce enough insulin to compensate. This results in higher blood sugar levels, which can affect both mother and baby if left untreated.

Pregnancy hormones (human placental lactogen, oestrogen, progesterone, cortisol and prolactin) contribute to this. When resistance rises beyond the body’s ability to compensate, blood glucose levels increase. Women are at greater risk if they were overweight before pregnancy (BMI >30 kg/m²), have a family history of diabetes, have had GDM in a previous pregnancy or have conditions such as polycystic ovary syndrome (PCOS).

"Poorly controlled GDM can lead to complications such as excessive fetal growth (macrosomia), birth trauma, neonatal hypoglycaemia (low blood glucose levels) and an increased risk of caesarean delivery."

GDM typically appears between 24 and 28 weeks of gestation, which is why this is the recommended screening period using an oral glucose tolerance test (OGTT). During the OGTT a 75 g glucose drink is given and blood sugar levels are checked while fasting, after one hour, and again after two hours. If results show levels above 5.1 mmol/L fasting, 10 mmol/L at one hour, or 8.5 mmol/L after two hours, GDM is diagnosed (American College of Obstetricians and Gynecologists, 2023).

Poorly controlled GDM can lead to complications such as excessive fetal growth (macrosomia), birth trauma, neonatal hypoglycaemia (low blood glucose levels) and an increased risk of caesarean delivery. For mothers, it can contribute to high blood pressure, preeclampsia and greater long-term risk of Type 2 Diabetes. Although GDM usually resolves after birth, women have up to a 50% increased risk of developing Type 2 Diabetes later in life (American Diabetes Association, 2024).

Effective management therefore not only supports a healthy pregnancy but also promotes long-term health for both mother and baby.

Nutritional management of GDM

Medical nutrition therapy (MNT) is the first-line approach for managing GDM and has been shown to improve glucose control, reduce the need for insulin and support optimal birth outcomes (McIntyre et al., 2019; ADA, 2024). The goal is to maintain blood glucose within target levels, ensure adequate nutrition for both mother and fetus, and promote healthy weight gain. Nutritional needs and carbohydrate portions should be individualised by a dietitian.

Energy needs vary depending on pre-pregnancy weight and activity level. Weight gain recommendations differ according to pre-pregnancy BMI:

Normal weight: 11.5–16 kg
Overweight: 7–11 kg
Obesity: approximately 6 kg (Institute of Medicine, 2009)

Carbohydrates should provide roughly 38–60% of total energy, with a minimum of 130 g per day to support fetal brain development (ADA, 2024). Carbohydrate-containing foods include starches, fruit, dairy, legumes and starchy vegetables. The focus should be on spreading carbohydrate intake evenly throughout the day—typically over three meals and two to three snacks—to prevent spikes and dips in blood glucose. Choosing low-glycaemic index (GI) options such as oats, legumes, sweet potato, and whole grains can further help stabilise blood sugar levels (Louie et al., 2021). Pairing carbohydrates with protein or healthy fats—such as nut butter with fruit or avocado on toast—also helps moderate post-meal glucose rises.

Added sugars and refined carbohydrates should be limited. Aim for products with <5 g sugar per 100 g and starches with >6 g fibre per 100 g. Fibre (20–35 g per day) supports blood glucose control, gut health and can help prevent constipation, a common pregnancy concern.

Protein requirements are slightly higher during pregnancy to support fetal growth and maternal tissue changes, with around 1.1 g/kg body weight recommended daily. Good sources include lean meat, fish, eggs, dairy, legumes and tofu. Fat intake should make up 20–35% of total energy, focusing on unsaturated fats such as olive oil, nuts, seeds, and avocado, while keeping saturated fats (e.g., visible fat on meat, butter, processed meats) to less than 10%.

Lifestyle and monitoring

Physical activity plays a vital role in improving insulin sensitivity and overall glucose control. Unless medically contraindicated, pregnant women with GDM are encouraged to do at least 150 minutes of low- to moderate-intensity exercise per week—for example, brisk walking or swimming (Ruchat et al., 2018). Even short walks after meals can help lower postprandial blood glucose levels.

However, it is important to consult your gynaecologist before starting or continuing exercise during pregnancy. If the length of your cervix is too short, certain forms of physical activity may not be recommended due to the risk of preterm labour.

"In addition to standard glucometers, Continuous Glucose Monitoring (CGM) systems can provide valuable insight by tracking glucose levels continuously throughout the day..."

At each scan, ask your gynaecologist where their baby’s growth is tracking on the growth chart. Keeping the baby’s growth closer to the 50th percentile is ideal. GDM often leads to macrosomia (large baby), as excess glucose passes through the placenta and umbilical cord, stimulating fetal insulin production and fat storage. Sudden jumps in growth percentiles should be checked and may mean the diet needs adjusting.

Close glucose monitoring is key to managing GDM effectively. Most gynaecologists request at least one week of blood glucose readings—including fasting and two-hour postprandial values—to confirm diagnosis and assess control. Thereafter, fasting readings are often continued to monitor trends and identify gradual increases over time.

In addition to standard glucometers, Continuous Glucose Monitoring (CGM) systems can provide valuable insight by tracking glucose levels continuously throughout the day and night. This helps identify patterns, assess responses to meals, and detect evening or post-meal spikes that may otherwise go unnoticed.

Keeping a food diary for the entire duration of pregnancy, may assists the dietitian in adjusting dietary intake to maintain glucose within target ranges. Monthly check-ins with a dietitian are strongly advised to adjust the diet throughout the pregnancy as needed.

For most women, blood glucose levels return to normal after birth. However, follow-up testing is essential, as women who have had GDM are at higher risk of developing Type 2 Diabetes. Maintaining healthy lifestyle habits—including balanced eating, staying active and achieving a healthy body weight postpartum—can significantly reduce this risk.

GDM can feel overwhelming, but with a well-structured diet, consistent glucose monitoring, appropriate activity and professional support, it can be managed successfully for a healthy pregnancy.

References

American College of Obstetricians and Gynecologists (ACOG) (2023) Gestational Diabetes Mellitus: Practice Bulletin No. 190. Washington, DC: ACOG.

American Diabetes Association (ADA) (2024 ) ‘15. Management of Diabetes in Pregnancy: Standards of Care in Diabetes—2024’, Diabetes Care, 47(Suppl. 1), pp. S254–S266.

Institute of Medicine (2009) Weight Gain During Pregnancy: Re-examining the Guidelines. Washington, DC: The National Academies Press.

Louie, J.C.Y. et al. (2021) ‘Low-glycaemic index diets in pregnancy: A systematic review and meta-analysis’, Nutrients, 13(3), 859.

McIntyre, H.D. et al. (2019) ‘Gestational diabetes mellitus’, Nature Reviews Disease Primers, 5(1), 47.

Ruchat, S.M. et al. (2018) ‘Effect of exercise on gestational diabetes mellitus: A systematic review and meta-analysis’, BJOG: An International Journal of Obstetrics & Gynaecology, 125(3), pp. 313–323.