The mother’s gut bacteria and diet appear to be crucial to promoting healthy pregnancy.

The study, published in the journal Nature Communications, showed that pregnancy outcomes and infant immunity are linked to gut bacteria.

Plant-based fibre is broken down in the gut by bacteria into factors that influence the immune system. The research team investigated the role of these metabolic products of gut bacteria during pregnancy.

The researchers found that in humans, reduced levels of acetate, which is mainly produced by fibre fermentation in the gut, is associated with the common and serious pregnancy-related condition preeclampsia.

Preeclampsia occurs in up to 10 per cent of pregnancies and is characterized by high blood pressure, protein in the urine and severe swelling in the mother’s body.

It also interferes with the child’s immune development whilst in the womb, with some evidence suggesting a link to higher rates of allergies and autoimmune diseases later in life.

The study found that preeclampsia affected the development of an important foetal immune organ – the generate which sits just behind the breastbone.

Foetuses in preeclamptic pregnancies were found to have a much smaller thymus than children from healthy pregnancies.

The cells the thymus normally generates  ‘T’ cells, and specifically those associated with the prevention of allergies and autoimmune conditions such as diabetes — also remained lower in infants after preeclampsia, even four years after delivery.

The mechanisms of acetate on the developing foetal immune system were further examined in separate experiments involving mice that showed acetate was central in driving foetal thymus and ‘T’ cell development.

The results showed that promoting specific metabolic products of gut bacteria during pregnancy might be an effective way to maintain a healthy pregnancy and to prevent allergies and autoimmune conditions later in life.