Women who had depressive symptoms during their third trimester of pregnancy, or persistently before and after giving birth, were twice as likely to have babies with very low levels of immunoglobulin A, an antibody that plays a crucial role in immunity.
Researchers published their findings in the journal Clinical & Experimental Allergy.
The study included 1043 mother-infant pairs from the Canadian Healthy Infant Longitudinal Development (CHILD) study. During and after their pregnancies, mothers completed questionnaires about their mood. Afterward, stool samples from their babies were examined for intestinal secretory immunoglobulin A.
Low concentrations of fecal immunoglobulin A were more common in infants of women who reported depressive symptoms during the antepartum period or persistently before and after birth, researchers found. Depressive symptoms did not have to be severe enough for a clinical diagnosis of depression to influence gut immunity in offspring.
The lowest levels of immunoglobin A were found in infants between 4 and 8 months old, researchers noted—a period when babies typically begin producing immunoglobulin on their own.
“The largest impact of depression in the mothers was seen in this startup phase of the child's own immune system,” said researcher and pediatric epidemiologist Anita Kozyrskyj, PhD, of the University of Alberta, Edmonton, Canada.
Lowered immunity, researchers explained, puts babies at increased risk of respiratory and gastrointestinal infections, asthma, and allergies. It could also elevate risk for depression, obesity, and autoimmune diseases such as diabetes.
“These findings should not be used to blame mothers,” Dr. Kozyrskyj said. “Maternal mental health does not occur in isolation.”