Q: I heard the uterine lining should be at least 8-9 mm thick for implantation. But how about the quality?

A: You are correct, endometrial thickness is an important aspect to assess (via ultrasound) to determine whether it's ready for implantation. Another quality of the lining is a characteristic healthy appearance — it should have a 'trilaminar' or a three-lined look that shows it is properly responding to the stimulation by estrogen. If the lining looks homogeneous or "whited out," it will not be hospitable to implantation.