Maternal Diet Predicts Risk of Premature Birth

Diet matters when it comes to preterm birth

Focus on eating better foods rather than avoiding junk foods

Lower maternal diet quality predicts higher risks of birth defects, gestational length, and other aspects of fetal development. Researchers in Spain used data from 787 expectant mothers to determine if fruit and vegetable intake predicted the length and weight of newborns. Both length and weight were expressed as the proportion of newborns whose length and weight were less than the 10th percentile of births in the general Spanish population, adjusted for length of gestation. This measure is called small for gestational age (SGA). Fruit and vegetable consumption information came from food frequency questionnaires for the first and third trimesters.

Compared to women in the highest quintile of vegetable consumption, women in the lowest quintile had 2.7 and 4.5 times higher risks of a SGA newborn for weight and length, respectively. These results reflected adjustment for confounding factors, including mothers’ gestational weight gain, smoking, and social class. Fruit consumption was not related to birth weight or length. Thus, expectant mothers who ramp up their vegetable intake might improve their own health and that of their newborn.

High stress diminishes executive function, which predicts unhealthy eating, overeating, weight gain, and obesity. Expectant mothers who experience high levels of stress might make poorer food choices than non-stressed mothers. Researchers recruited 353 low-income pregnant women with an average age of 25.7 years from Special Supplemental Nutrition for Women, Infants, and Children at four locations in Michigan to determine if stress levels affected food choices. The Perceived Stress Scale evaluated stress over the previous month with responses to nine items on a four-point scale. Fat, fruit, and vegetables intakes were assessed with the Rapid Food Screener. High, as opposed to low, stress predicted significantly lower intake of fruit and vegetables, even after accounting for confounding factors. Fat intake was not related to stress level. Given the effect of a poor maternal diet on fetal and newborn health, helping pregnant women deal effectively with high stress should be a public health priority.

Overweight predicts increased risk of premature birth. Thus, diet during pregnancy might also predict risk of premature birth. Researchers in Norway used data from 66,000 pregnant women in the Norwegian Mother and Child Cohort Study to address this idea. Food intake of the participants was classified according to three dietary patterns: prudent, traditional, and western. The prudent pattern emphasized vegetables, onions, fruit, nuts (among others) and de-emphasized processed meat, white bread, and pizza. The traditional diet emphasized boiled potatoes, fish, gravy, margarine, low-fat milk (among others) and de-emphasized poultry and pizza. The western diet emphasized salty snacks, chocolate and sweets, French fries, white bread, processed meat, and pasta, while de-emphasizing fish and fiber-rich bread.

Compared to women in the lowest one-third of adherence to the prudent diet, those in the highest one-third showed a significant 12 percent lower risk of any type of premature birth. Similarly, compared to women in the lowest one-third of adherence to the traditional diet, those in the highest one-third showed a significant 9 percent lower risk of any type of premature birth. The risk declined further for late-preterm delivery. All analyses adjusted for ten confounding factors, including maternal age, smoking, and previous preterm birth. Adherence to the western dietary pattern did not predict risk of preterm delivery. This study has two messages for pregnant women: 1) Focus on improving your diet, and 2) pay less attention to avoiding junk food.

A recent systematic review investigated links between maternal diets and risk of preterm birth and small for gestational age (SGA) birth. Researchers in Australia identified 40 studies that met their inclusion criteria. The studies varied widely in quality, assessments of dietary patterns, and assessments of birth outcomes. Thus, the researchers conducted a systematic review rather than a meta-analysis. Overall, the evidence suggested that maternal diet affects risk of premature and SGA births. Maternal diets during pregnancy that predicted lower risk of preterm birth varied but generally featured high intakes of vegetables, fruits, whole grains, fish, and dairy products. Similarly, maternal diets during pregnancy that predicted lower risk of SGA birth typically included high intakes of vegetables, fruits, legumes, fish, and milk products.

The findings of the above studies reprise long-standing advice from nutritionists to eat better to reduce risk of chronic diseases, such as cardiovascular disease, type 2 diabetes, and cancer. Pregnant women can do themselves and their forthcoming children a favor by improving the quality of the foods they eat. How about eating just one more serving of vegetables each day?

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