During pregnancy, many women get food cravings, hear that they should “eat for two,” and often talk about what is healthy for the baby while it is still growing in the belly.
A study from the Institute of Agrochemistry and Food Technology (IATA) of the Spanish National Research Council (CSIC), with participation from the Hospital Doctor Peset in Valencia, reveals that the Mediterranean diet promotes a vaginal microbiome more conducive to pregnancy in women undergoing artificial insemination.
The research team studied the vaginal bacteria of 104 women aged 18 to 38 who had difficulty getting pregnant after trying for 12 months or more. They also checked how closely these women followed the Mediterranean diet using a tested questionnaire.
The results show that women who follow the Mediterranean diet present microbial profiles more favourable for embryo implantation and pregnancy maintenance.
The work, published in the scientific journal Food & Function, shows that women who became pregnant had a vaginal microbiota (microorganisms in the vagina that are key to reproductive health) that was less diverse and dominated by bacteria of the genus Lactobacillus. They are associated with a more stable and healthy environment.
In contrast, those who did not achieve pregnancy, especially with low adherence to the Mediterranean diet, showed a higher presence of bacteria such as Gardnerella vaginalis, linked to microbial imbalances.
The study also found differences in the vaginal bacteria of women whose pregnancies went to full term compared to those who had a miscarriage. This suggests that the types of bacteria in the vagina, which can be partly affected by diet, may be important for getting pregnant and for a healthy pregnancy.
“A lower vaginal microbial diversity during pregnancy, unlike what happens with the gut microbiota, does not necessarily imply an imbalance, but is usually associated with a state of stability and health, especially when Lactobacillus bacteria predominate,” explains Mª Carmen Collado, CSIC researcher at the Mainbiotics laboratory of IATA and leader of the study.
Bacteria that promote reproductive health
The team classified each woman’s vaginal microbiota into different types of microbial communities according to the dominant microorganisms.
They paid special attention to the genus Lactobacillus, bacteria that act as a protective shield for the vaginal environment and promote reproductive health.
This information was compared with what the women ate and their pregnancy results using a computer program that can find patterns and show which factors are most important for getting pregnant.
The study suggests that what people eat could help improve the success of fertility treatments. This is important because a Western lifestyle, with stress, unhealthy food, and antibiotic use, can disturb the balance of vaginal bacteria and affect women’s fertility.
A new way to predict reproductive outcomes
The study reveals that certain microbial profiles may help anticipate reproductive outcomes in assisted reproduction, although these associations must be interpreted with caution.
Manuel Bernabéu, postdoctoral researcher at IATA and co-author of the study
In the group studied, the bacterium Gardnerella vaginalis was found more often in women who did not get pregnant and did not follow the Mediterranean diet closely. This bacterium is linked to a common vaginal infection and has been connected to lower chances of pregnancy and higher infertility.
Some micronutrients abundantly present in Mediterranean diet foods—such as vitamins A, C, D, and E, beta-carotene, calcium, and zinc—“appear to play a protective role against bacterial vaginosis, the most common vaginal disorder in women of reproductive age, characterized by an imbalance in the vaginal microbiota,” explains Mar Gimeno, specialist in Gynecology and Obstetrics at the University Clinical Hospital of Valencia, formerly at Hospital Dr. Peset and co-author of the study.
Moreover, among participants who achieved pregnancy, those who later experienced miscarriage showed different microbial profiles, with lower levels of Lactobacillus, which “is consistent with evidence linking vaginal microbiota alterations to the risk of early pregnancy loss,” says Martina Baizán Urgell, predoctoral researcher at IATA and first author of the study.
How to improve fertility outcomes?
“It is necessary to confirm these findings with larger studies, but the data suggest that intervening in lifestyle habits, such as diet, could become a complementary strategy to improve outcomes in assisted reproduction. In addition, this study opens the door to considering the vaginal microbiota as a potential predictive marker of fertility,” says Elia García Verdevio, gynecologist participating in the study.
Eating lots of fruits, vegetables, beans, whole grains, fish, and olive oil, which is typical of the Mediterranean diet, helps keep the balance of vaginal bacteria healthy.
“Eating a healthy diet can be something we can change to help improve fertility treatment success by supporting better bacteria balance,” says Carmen Collado.
“Although the results are promising, it is necessary to increase the sample size and conduct longitudinal studies to confirm these findings and facilitate their clinical application,” concludes the research team.
07.05.2025.
