If the fertilized egg is in the uterine fundus, the left wall, right wall, anterior wall and posterior wall of the uterus are all very good locations for the implantation. However, if the fertilized egg is deposited close to the uterine horn, with the further enlargement of the gestational sac towards the uterine horn, it is likely to result in a uterine horn pregnancy, which will cause severe lower abdominal pain in the clinic, or even uterine rupture resulting in massive bleeding, which puts the patient’s life at great risk. If the gestational sac settles close to the uterine orifice, repeated vaginal bleeding will occur, triggering preeclampsia. With further development of the gestational sac and formation of the placenta, it is likely to form a low lying placenta, or placenta praevia. Therefore, clinically, it is relatively bad whenever the placenta is placed near the uterine horn, or near the uterine opening.