“The quality, not just quantity, of what a woman eats during pregnancy may greatly affect her health, and the long-term health prospects of her child,” Dr. David S. Ludwig commented via email.
Dr. Ludwig, with Children’s Hospital Boston and Harvard Medical School, and colleagues say that there’s little evidence to recommend any specific diet when pregnancy is complicated by excessive weight, which “exacerbates insulin resistance and related metabolic aberrations.” This in turn may alter intrauterine development in ways that affect the offspring for a lifetime.
These adverse factors may be ameliorated with a low-glycemic load (GL), the authors postulated. Glycemic load, they explain, is calculated by multiplying the amount of dietary carbohydrate by its glycemic index (GI), which describes the rise in blood glucose after a meal.
The researchers investigated the effects of a low-GL versus a low-fat diet in 46 pregnant women with BMIs greater than 25 and less than 45. The low-GL diet reduced total carbohydrates moderately and replaced higher GI carbohydrates with lower GI carbohydrates.
“A diet rich in unprocessed carbohydrates (e.g., vegetables, fruits, beans and whole grains), healthy fats (e.g., olive oil, nuts, avocado) and adequate protein lowers cardiovascular disease risk in the mother, and may prevent premature delivery and improve infant brain development,” Dr. Ludwig said.
The primary outcome of the study was birth weight, and other endpoints included infant anthropometric measurements, pregnancy duration and maternal metabolic parameters.
There was no significant difference between the groups in infant birth weight z scores or ponderal index, according to the report. Head circumference, however, was greater in the low-GL arm (35.0 cm) than in the low-fat arm (34.2 cm; p=0.01).
Gestational age was significantly longer in the low-GL group (39.3 weeks) than in the low-fat group (37.9 weeks; p =0.05), and rates of delivery before 38 weeks were 5% versus 53% in the two groups, respectively, after excluding planned cesarean deliveries.
Maternal cardiovascular risk factors were improved too with the low-GL diet compared with the low-fat diet. For example, increases in triglycerides in the two groups were 49 mg/dL vs 93 mg/dL, respectively, while C-reactive protein dropped 2.5 mg/dL vs. 0.4 mg/dL.
“Large-scale studies are warranted to evaluate whether dietary intervention during pregnancy aimed at lowering GL may be useful in the prevention of prematurity and other adverse maternal and infant outcomes,” the authors conclude.
Dr. Ludwig added, “Pregnancy may be the optimal time to prevent obesity and other chronic diseases in the next generation.”
Effects of a low–glycemic load diet in overweight and obese pregnant women: a pilot randomized controlled trial
Am J Clin Nutr 2010.