If you have a history of depression or anxiety, you might be at increased risk of the same during pregnancy. While the use of antidepressants during pregnancy in the US has increased from 2% in 1997 to over 7% in 2008, in a controversial review, 

the Journal of the American Medical Association Pediatrics suggested that taking antidepressants during pregnancy could double the child’s risk of autism, from about 1% to 2%. 

However, a growing body of research suggests that probiotics could be safe and effective in treating pregnant women (and their respective newborns), as stress resulted in higher levels of pathogenic bacteria in both mother and newborn with lower levels of healthy bacteria. Babies born of high stress mothers are more likely to have allergies, intestinal disorders with negative impacts on the brain, and behavior development (stress and the commensal microbiota, Tamra L. Gur, 2/15).

In 2011, a peer reviewed study showed, that 30 days after taking two strains of “good” bacteria—Lactobacillus helveticus and Bifidobacterium longum—subjects showed decreased anxiety, depression, anger, and hostility, perhaps because these bacteria release substances that reduce inflammation.