A recent study published in the European Journal of Clinical Nutrition examined the association between an increasing trend towards plant-based dietary patterns among Iranian pregnant women and the risk of excessive or inadequate gestational weight gain.
Gestational weight gain is an important health marker for the health of the mother and the fetus during pregnancy. It is a physiological response during pregnancy due to gestational fat deposition and fetal development. It is strongly correlated to the development of the fetus and the health outcomes of the child, with studies showing that inadequate gestational weight gain often results in low bright weight in infants, as well as intrauterine growth retardation. On the other hand, excessive gestational weight gain increases the risk of preterm delivery and predisposes the infant to childhood obesity.
Gestational weight gain can be regulated through maternal diet, and recent studies have shown that the macronutrient composition and energy content of maternal diets are strongly linked to the magnitude of weight gained during pregnancy. Furthermore, recent research in nutritional epidemiology has focused more on analyzing dietary patterns rather than single nutrient intake since it is a better health outcome predictor. Given that the popularity of vegetarian and plant-based diets is increasing, especially among young women, it is vital to understand the impact of such diets on gestational weight gain.
About the study
In the present study, the researchers calculated three dietary indices — plant-based dietary index, healthy plant-based dietary index, and unhealthy plant-based dietary index by assigning differing scores to healthy and less healthy food groups that were plant-based and animal-based food groups. They examined a prospective cohort of pregnant women in Iran to understand the relationship between the risk of excessive or inadequate gestational weight gain and these dietary indices.
This study was part of the Persian Birth Cohort study conducted in five Iranian districts to gather knowledge and scientific evidence for developing policies on various developmental aspects of diseases by examining the impact of lifestyle, socioeconomic factors, and the environment on gestational outcomes.
The present study recruited women from healthcare centers in the city of Semnan from 2018 to 2020. Women who had been residing in the city for at least a year, were in the first trimester of pregnancy, and intended to deliver their baby in one of the hospitals in the city were eligible to participate in the study. While pregnancies that ended in normal and cesarian deliveries were included in the study, women undergoing hormone therapy or having a hormonal disease or twin gestations were excluded from the study.
The dietary indices were calculated by assigning different scores to different food types, and the dietary habits of the participants were assessed using a food frequency questionnaire containing 90 items. Maternal weight was measured after each trimester and before delivery, and gestational weight gain was calculated by subtracting the first-trimester weight from the last measured weight before delivery. Based on the body mass index before pregnancy, gestational weight gain was classified as adequate, excessive, or inadequate.
Information on other variables, including demographic characteristics, disease history, education levels, physical activity levels, vitamin supplementation, and socioeconomic factors, were obtained during interviews.
The findings showed that an increased adherence to plant-based dietary patterns decreased the risk of inadequate gestational weight gain. The relationship between the plant-based dietary index and inadequate gestational weight gain was negative. However, no significant associations were observed between the other two dietary indices and inadequate gestational weight gain. Excessive gestational weight gain showed no relationship with any of the dietary indices.
The study found that, as recommended by the American Dietetic Association, a higher inclusion of fruits, legumes, vegetable oils, and vegetables, along with fish, decreased the risk of inadequate weight gain during gestation. The researchers believe that the lack of observed associations between any of the dietary indices and excessive gestational weight gain could be due to the small study population.
The potential mechanism through which plant-based diets might help regulate gestational weight gain is based on the fiber content of plant-based diets. The high dietary fiber content of vegetables, fruits, nuts, and cereals regulates hunger by increasing the secretion of satiety hormones, which in turn helps control body weight. It also helps regulate postprandial insulin and subsequent fat oxidation.
Overall, the findings reported that an increased adherence to plant-based foods was associated with a lower risk of inadequate gestational weight gain. No associations were observed between the plant-based dietary indices and excessive gestational weight gain, and further studies across larger cohorts are required to understand the association between dietary patterns and gestational weight gain.