The cause of chorionic villus bulge in early pregnancy is not very clear at present, it may be due to the occurrence of pre-miscarriage, or it may be related to the chromosomal abnormality of the embryo and so on. Chorionic villus bulge is a rare abnormality in early pregnancy, which refers to a localized irregular bulge of the chorionic villus on the surface of the underlying meconium towards the gestational sac, and the probability of its occurrence is extremely low. The cause of chorionic villus bulge is not very clear, it may be related to the following two factors. 1. Pre-eclampsia. The prevailing theory is that the chorionic villus bulge may be due to bleeding or the formation of a hematoma. When there is a miscarriage with preeclampsia, hemorrhage may occur, which may lead to chorionic villus elevation. 2. Chromosomal abnormalities in the embryo. Another possible cause of chorionic villus elevation is chromosomal abnormalities in the embryo. If the embryo has chromosomal abnormalities, chorionic edema and interstitial edema may lead to localized enlargement of the placenta, and chorionic villus bulging may appear on ultrasound.