Does the endometrium thicken during early pregnancy?

In the first pregnancy, B ultrasound examination can not see the pregnancy sac, found endometrial thickening, such as in clinical endometrial thickness greater than 1.3cm, there is a history of menstrual arrest, is pregnancy caused by endometrial thickening, early pregnancy endometrial thickening is normal phenomenon. When there is a history of menstrual arrest, after B ultrasound examination found endometrial thickening, blood HCG or urine HCG positive, the possibility of pregnancy is very large.