Pigmentary demarcation lines (PDLs) are rare pigmentary diseases with abrupt transition lines bet ween areas of deeper pigmentation and areas of lighter or normal pigmentation. Among several types, type B PDL involves the posterior medial part of the lower extremities and is commonly associated with pregnancy. In South Korea, only a few cases of type B PDL during pregnancy is reported; how ever, here we present a case of recurrent type B PDL during pregnancy. The patient experienced 2 pregnancies with pigmentary changes in the posterior thigh from the late second trimester; the pigmentation faded and disappeared a few months after delivery in both pregnancies. Most PDLs are asymptomatic and are spontaneously relieved. It will be helpful for obstetricians to recognize this condition and reassure patients.