Following a Mediterranean-style diet during pregnancy reduce risk of developing preeclampsia


Following a Mediterranean-style diet during pregnancy was associated with a reduced risk of developing preeclampsia, and Black women appeared to have the greatest reduction of risk, according to new research published today in the Journal of the American Heart Association.

Previous studies have found that following a Mediterranean diet, which consists primarily of vegetables, fruits, legumes, nuts, olive oil, whole grains, and fish, reduces heart disease risk in adults.

Preeclampsia, a condition during pregnancy characterized by severe high blood pressure and liver or kidney damage, is a major cause of complications and death for the mother and her unborn child. Preeclampsia also increases a woman’s risk of heart diseases, such as high blood pressure, heart attack, stroke or heart failure, by more than two times later in life.

Women with preeclampsia have a higher risk of preterm delivery (giving birth before 37 weeks gestation) or low birth weight babies, and children born to mothers with preeclampsia are also at higher risk of developing high blood pressure and heart disease.

Black women are at higher risk of developing preeclampsia, yet research on potential treatments for high-risk women are limited, according to the study researchers. The researchers investigated the potential association of a Mediterranean-style diet among a large group of racially and ethnically diverse women who have a high risk of preeclampsia.

“The U.S. has the highest maternal mortality rate among developed countries, and preeclampsia contributes to it,” said Anum S. Minhas, M.D., M.H.S., chief cardiology fellow and a cardio-obstetrics and advanced imaging fellow at Johns Hopkins University in Baltimore. “Given these health hazards to both mothers and their children, it is important to identify modifiable factors to prevent the development of preeclampsia, especially among Black women who are at the highest risk of this serious pregnancy complication.”

This study included data for more than 8,500 women enrolled between 1998 and 2016 in the Boston Birth Cohort. Participants’ median age was 25 years old, and they were recruited from Boston Medical Center, which serves a predominantly urban, low-income, under-represented racial and ethnic population.

Nearly half of the participants were Black women (47%), about a quarter were Hispanic women(28%) and the remaining were white women or “other” race, according to self-reported information on a postpartum questionnaire. Researchers created a Mediterranean-style diet score based on participants’ responses to food frequency interviews and questionnaires, which were conducted within three days of giving birth.

The analysis found:

  • 10% of the study participants developed preeclampsia.
  • Women who had any form of diabetes before pregnancy and pre-pregnancy obesity were twice as likely to develop preeclampsia compared to women without those conditions.
  • The risk of preeclampsia was more than 20% lower among the women who followed a Mediterranean-style diet during pregnancy.
  • Black women who had the lowest Mediterranean-style diet scores had the highest risk (78%) for preeclampsia compared to all other non-Black women who more closely adhered to the Mediterranean-style diet.

“We were surprised that women who more frequently ate foods in the Mediterranean-style diet were significantly less likely to develop preeclampsia, with Black women experiencing the greatest reduction in risk,” Minhas said. “This is remarkable because there are very few interventions during pregnancy that are found to produce any meaningful benefit, and medical treatments during pregnancy must be approached cautiously to ensure the benefits outweigh the potential risks to the mother and the unborn child.”

Minhas added, “Women should be encouraged to follow a healthy lifestyle, including a nutritious diet and regular exercise, at all stages in life. Eating healthy foods regularly, including vegetables, fruits and legumes, is especially important for women during pregnancy. Their health during pregnancy affects their future cardiovascular health and also impacts their baby’s health.”

The study’s limitations are related to the food frequency interviews: they were conducted once after the pregnancy, and they relied on self-reported information about which foods were eaten and how frequently they were eaten.

Gastrointestinal (GIT) microbiota play a role in protecting or promoting adverse pregnancy outcomes. GIT microbial dysbiosis, as defined as low alpha diversity and reduced levels of butyrate producing bacteria, is associated with bacterial translocation and the promotion of endotoxins, creating systemic inflammation.

Such inflammation may lead to preterm labor [1], higher blood pressure [2], and increase the risk of developing gestational diabetes [3]. Thus, improving GIT microbial health may help to mitigate adverse pregnancy outcomes.

At baseline, a normal GIT microbial community shifts throughout pregnancy. There is a natural decline in butyrate-producing bacteria from the Firmicutes (Coprococci, Eubacterium, Roseburia, and Faecalibacterium genera) and Bacteroidetes (Odoribacter and Alistipes genera) phyla [2] at the end of gestation.

Bifidobacteria, Proteobacteria, and lactic acid–producing bacteria increase during the third trimester. This process is thought to help facilitate the normally observed increase in inflammation and weight gain to increase energy supply for the fetus [4]. The end result is less alpha diversity and Operational Taxonomic Unit (OTU) richness by the end of the third trimester.

Several studies demonstrate that at this point, the composition resembles that of an individual with metabolic syndrome, with increased Actinobacteria and Proteobacteria, and decreased Faecalibacterium [4, 5]. The rate at which these changes occur and the degree to which alpha diversity changes may play a role in avoiding preterm birth, preeclampsia, or other adverse pregnancy outcomes.

Furthermore, manipulating microbial diversity over time may be possible with targeting maternal diet.

Several diet patterns have been associated with improved GIT microbial profiles. Vegetarian diets promote higher levels of roseburia and lacnospiraceae, and reduce collinsella, which is associated with higher levels of circulating insulin [6] [7].

Proportions of high fiber and low-fat intake are correlated with greater microbial diversity and lower levels of bacteriodaceae [8].

Polyunsaturated fatty acids also promote gut mucosal integrity and insulin sensitivity by inhibiting inflammation through byproduct fermentation [9]. Particular interest lies in the Mediterranean diet pattern (MDP), which is characterized by high amounts of fiber, lean proteins, fruits and vegetables, and lower consumption of red meats and processed foods.

Several studies have noted a beneficial association with consumption of an MDP and GIT microbiome characteristics. MDP adherence is associated with lower levels of lower Escherichia coli, higher amounts of bifidobacteria, and greater amount of bacterial richness. Such a composition leads to high levels of fecal short-chain fatty acids that contribute to epithelial connections, reduce bacterial translocation and improve systemic inflammation which would otherwise lead to chronic disease [10,11,12,13].

Mediterranean diet patterns are also associated with improved maternal and neonatal outcomes including a lower chance of diabetes [14], hypertension during pregnancy [15], excessive gestational weight gain, low birth weight neonates [16], and beneficial metabolic profiling in offspring [17] [18].

The impact of an MDP has not been thoroughly evaluated on the gastrointestinal microbiome during pregnancy. The relationship of improved metabolic health with a Mediterranean diet via increased GIT microbial diversity is established in non-pregnant populations [8] [19], but gaps in knowledge of this relationship among parous women remain.

To better understand this relationship, we tested the hypothesis that better adherence to an MDP is associated with higher microbial diversity during pregnancy.

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More information: Journal of the American Heart Association (2022).



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