WASHINGTON — Dietary guidance in pregnant individuals with diabetes should be “reframed” with a comprehensive approach to glycemic optimization and consideration of placental — not only fetal and maternal — energy needs, Amy Valent, DO, MCR, of the Oregon Health & Science University, advised at the biennial meeting of the Diabetes in Pregnancy Study Group of North America (DPSG-NA).

Glycemic optimization should include “not just what you eat but when you eat and how you eat it,” she said, referencing studies on food order and carbohydrate distribution that she said are small but worthy of consideration when counseling patients.

Flexibility in carbohydrate intake during pregnancy may be warranted for several reasons, she said, including the fact that the current Recommended Daily Allowance (RDA) for carbohydrates in pregnant individuals — ≥ 175 g/d — was developed in 2005 to account for maternal and fetal brain glucose requirements but not the needs of the placenta.

“We’ve commonly forgotten about the placental demands (for fuel),” Valent said in an interview after the meeting. “We appreciate all the work the placenta does, but we don’t appreciate how much energy it has to have. And we clearly haven’t accommodated for that in our [nutritional] guidelines.”

Data published in recent years show the rate and amount of placental glucose consumption in humans, and this information has enabled development of a proposed new recommendation for carbohydrate intake during pregnancy — ≥ 220 g/d — which accounts for placental glucose consumption, said Teri L. Hernandez, PhD, RN, of the University of Colorado Anschutz College of Nursing in Aurora, Colorado, at the DPSG-NA meeting.

Hernandez and Paul J. Rozance, MD, also of the University of Colorado Anschutz, described their calculations for the modified RDA and the supporting research on placental glucose utilization in a narrative review paper published in 2023.

Other research led by Hernandez has focused on gestational diabetes (GD) and looked at outcomes with a diet of liberalized complex carbohydrates.

“Dr Hernandez’s work is very thoughtful,” Valent said. “It’s been helpful in demonstrating that we really should be more balanced, that we don’t have to be so restrictive with carbs.”

Advising Patients in Practice

In her clinical practice, Valent said, she commonly sees pregnant patients with GD or non-insulin-treated preexisting diabetes withdraw from eating carbohydrates until they’re counseled otherwise.

“If people see that their sugar spikes after they eat a banana, they don’t want to eat a banana again, even though [it contains] so many nutrients,” she said at the meeting. “But are there unintended consequences for the fetus by [removing] these nutrients? And can we instruct patients in a way where we can help their bodies metabolize glucose better?”

Simple interventions such as a carbohydrate-last food order could be considered, Valent said. Thus far, there are few data on pregnant individuals on the effects of the timing of carbohydrate consumption during a meal. Outside of pregnancy, research is growing, and a recently published crossover study of 20 nonpregnant adults with type 2 diabetes is noteworthy, she said, because it utilized continuous glucose monitoring (CGM) to gather detailed glycemic profiles and it included eating outside of a controlled setting.

Participants ate either carbohydrates-last or carbohydrates-first meals for 6 days followed by the reverse for another 6 days. The first 5 days of each period occurred in “free-living” conditions, and the sixth day was monitored in controlled conditions. No “rest interval” between meal components was required. Meals were provided and contained 45%-50% carbohydrates.

Participants had significantly greater time in range and improved glycemic variability during the carbohydrates-last intervention arm — and not only on the controlled day, Valent said.

Another study on the distribution of carbohydrate intake throughout the day found slightly higher glycemic variability in 12 patients with diet-treated GD, significantly lower mean glucose and fasting blood glucose, and significantly improved insulin sensitivity when they ate a diet with high carbohydrate in the morning (50% of carbohydrates) than when carbohydrate intake in the morning was lower, Valent noted.

In her own research, Valent has been analyzing CGM data from patients with GD to examine how the timing of meals relative to circadian rhythms can affect glycemia. An analysis expected to be published soon looked at early vs late breakfast eaters and found glycemic improvements — especially with respect to nocturnal glycemia — associated with earlier breakfast, she shared at the meeting.

Pending the collection of more data on food order in pregnancy and on what’s being coined “chrononutrition” in the literature, Valent said that her general approach with patients is to understand both their eating and glycemic patterns and to offer individualized suggestions for optimizing glycemic management.

“We see them so frequently during pregnancy that we have good opportunities to ask, what changes worked well this time? How did eating your proteins first go?” she said. Or for someone whose glucose spikes after eating cereal, for example, “we can reinforce the advice to make it part of a mixed meal with some good fats and proteins.”

Emphasizing the quality of carbohydrates — the value of whole grains and complex carbs — over limiting the quantity is key, as is a focus on the “nutritional/food health forest, and not just the glucose tree,” Valent said at the meeting. “We tend to be glucose centric,” she said. “But I think we can be more.”

The Case for Flexibility in Dietary Carbohydrate Content for GD

“Flexibility in carbohydrate content doesn’t mean increased calories, and it doesn’t mean increased simple sugars,” Hernandez said at the meeting. “What it does mean is a focus on the overall nutritional pattern and on increased complex carbohydrates.”

Hernandez became interested in nutrition therapy in GD after observing as a nurse how “terrifying” and “mentally taxing” a diagnosis of GD can be. The diagnosis and subsequent rigid restriction of carbohydrates made some patients “so fearful of a big baby that they reasoned they weren’t going to eat carbohydrates,” she said. “I saw a pattern of anxiety and depression.”

Perhaps surprisingly, carbohydrate restriction as a primary approach to dietary treatment of GD lacks rigorous evidence, Hernandez said, referring to analyses such as a 2017 Cochrane Database systematic review of types of dietary advice for pregnant women.

In a study published in 2023, Hernandez; Linda A. Barbour, MD, MSPH; and other researchers randomly assigned 59 women with GD to a higher-carbohydrate (60%) and lower-fat (25%) diet coined the CHOICE diet (Choosing Healthy Options in Carbohydrate Energy) or a conventional lower-carbohydrate (40%) and higher fat (45%) diet for 7-8 weeks. The diets were eucaloric, with a difference in carbohydrate intake of about 100 g/d.

The study found no differences between the two eucaloric diets in newborn adiposity, cord C-peptide level, maternal 24-hour glycemia, percentage time in range, or insulin resistance. Total gestational weight gain and weight gain during the intervention were similar.

When evaluating carbohydrate intake in pregnancy, Hernandez said, there are several things to consider, including the fact that glucose moves across the placenta via facilitated diffusion (ie, movement depends on higher maternal glucose relative to fetal glucose) and the potential for carbohydrate restriction to worsen micronutrient deficiency or promote ketonemia by increasing the glucagon to insulin ratio.

Moreover, low-carbohydrate diets typically have more calories from fat and/or protein, she said, and higher maternal lipids (triglycerides, free fatty acids) have been associated with fetal overgrowth.

Valent disclosed that she has institutional research funding from Dexcom and MannKind and does consulting (without compensation) for Dexcom, MannKind, and Janssen Research & Development. Hernandez reported having no conflicts of interest.