Yoga exercises undertaken during the maternity period may reduce unpleasant symptoms during pregnancy and reduce delivery pain. Flexibility of the hip joint improves the degree of pubic arch created in an open-leg posture and widens the pelvic outlet region, shortening the time required for delivery and facilitating easy delivery. The degree of pubic arch is related to the flexibility of the hip joint. Although many studies have shown the effect of yoga exercise during pregnancy, the effect on the degree of the pubic arch has not been elucidated. To elucidate whether the degree of the pubic arch is improved by yoga exercise during pregnancy, this study enrolled 177 pregnant subjects. The degree of pubic arch pre– and post–yoga exercise was measured using instruments in an open-leg posture (seated with femurs abducted). The mean pubic arch pre- and post-yoga was 122.61 and 127.93 degrees, respectively. The degree of pubic arch post–yoga sessions was significantly increased compared with pre–yoga sessions (p < 0.01). This study showed that yoga exercises during the pregnancy period appear to improve the degree of pubic arch.