Almost 25% of women experience a psychological disorder during pregnancy or after birth. Depression is the most common health problem, followed by anxiety. These disorders can have a profound impact both on women and their children, hindering the development of the bond between the two.

According to a recent study led by researchers at Radboud University (Netherlands), maternal psychological distress after birth can affect a child’s gut microbiota development and thus, their overall health. And the researchers, who published their results in Frontiers in Microbiology, suggest the origin could be found in maternal milk microbiota.

Current knowledge suggests that microorganisms in the maternal gut migrate to the mammary glands. Through maternal milk they arrive in the baby’s digestive tract. There, they take part in seeding the infant’s gut, activating and stimulating (like a training) the baby’s immune system and helping them mature their gastrointestinal tract.

The more diverse the bacteria passing from the maternal milk to the infant, the better for the newborn’s overall gut health. In fact, less varied bacteria in the maternal milk microbiota composition may contribute to lowering bacterial diversity in the infant gut. And, as we have explained in this blog before, reduced gut microbiota diversity in early life has already been linked to an increased risk of asthma, allergies and even metabolic disorders during infancy and adulthood.

To elucidate whether maternal psychological health influences an infant’s overall health—and if so, understanding how and to what extent—Dutch researchers set out a study that was part of a wider project called BINGO, the Dutch acronym for Biological Influences on Baby’s Health and Development. BINGO is a longitudinal cohort study that focuses on prenatal and early postnatal influences on infant health and development.

Reduced gut microbiota diversity in early life has already been linked to an increased risk of asthma, allergies and even metabolic disorders during infancy and adulthood.

The study involved 77 healthy women who delivered their babies at a mean gestational age of 39.7 weeks, all breastfed and none took antibiotics after delivery. Researchers took samples of milk 2, 6 and 12 weeks after the babies were born. Mothers, who didn’t suffer from serious postpartum distress, filled in mood questionnaires on any stress, anxiety and depressive symptoms experienced at 6 weeks postpartum.

“We saw that mothers with higher postnatal stress had a lower milk bacterial diversity when their babies were 3 months old,” told Caroline de Weerth, Professor of Psychobiology of Early Development at Radboud University Medical Center and senior author of the paper. “Diversity was not significantly different at 2 and 6 weeks postpartum and we don’t know why this was so,” she continues. “It is, however, possible that postnatal stress increased towards 3 months—our measures of stress are from 6 weeks postpartum—and that this is why differences in maternal milk microbiota diversity were only seen then,” she added.

According to the authors, the difference in bacterial diversity in the maternal milk microbiota 3 months after delivery may be at least partly driven by changes in the maternal gut microbiota. They hypothesized that psychological distress after birth could alter gut microbiota—and hence milk microbiota—through the gut brain axis and the stress control system, which is a complex network of hormonal interactions highly active in women with distress.

Psychological distress after birth could alter gut microbiota—and hence milk microbiota—through the gut brain axis and the stress control system.

This study provides early evidence of a possible mechanism through which postpartum psychological symptoms may affect infant development and health. Nevertheless, the authors highlight that, as a small study, further research is needed to clarify the relationship between maternal psychological distress and milk microbiota and any underlying mechanisms related to this connection.

Reference:

Browne D.P., Aparicio M., Alba C. et al. Human Milk Microbiome and Maternal Postnatal Psychosocial Distress. Frontiers in Microbiology, 2019. doi: 10.3389/fmicb.2019.02333

Cristina Sáez
Cristina Sáez
Cristina Saez is a freelance science journalist. She works for several media, for instance the Spanish newspaper La Vanguardia, where she coordinates the science section, Big Vang; as well as research centres and scientific societies. She has been awarded for her journalistic work, among others, with the Boehringer Ingelheim Award in Medical Journalism 2015. Follow Cristina on Twitter @saez_cristina