It is normal for the gestational sac to be found on the right side of the uterine cavity by ultrasound. It is normal as long as the fertilized egg enters the uterine cavity and lays on the floor of the uterus, on the posterior wall of the uterus, or on the left or right wall of the uterus. However, the following cases are abnormal: although it is in the uterine cavity, if it is near the endometrium, it often results in a low-set placenta and irregular vaginal bleeding may occur in early pregnancy. Also if the implantation is near the horn of the uterus, close observation must be given. As the gestational sac increases in size, if it extends towards the horn of the uterus, it is likely to result in a horn pregnancy, which must be reviewed regularly.