We further examined the amount of Tregs (CD4+CD25+Foxp3+) between the two groups before, during, and after antiviral intervention and found that the number of Tregs in AF mothers was significantly higher than that in NAF mothers before antiviral intervention (i.e. at 26–28 weeks gestation) (p = 0.02). Here, CD4 is linked to atrial fibrillation.