Please assess the completion status of the following clinical trial:

Trial Title: Expression of Endometrium During Window of Implantation

Study Design Characteristics:
- Allocation: None
- Intervention Model: None
- Observational Model: COHORT
- Primary Purpose: None
- Time Perspective: PROSPECTIVE
- Masking: None
- Phase: None
- Number of Arms: None

Eligibility Criteria:
Inclusion Criteria:~* Age: 30-44 years~* BMI: 18\~30 kg/m2~* Implantation failure at least two times~Exclusion Criteria:~* Primary ovarian insufficiency~* Congenital uterine anomaly~* Severe intrauterine adhesion~* Malignancy~* Donor cycle

- Gender: FEMALE
- Minimum Age: 30 Years
- Maximum Age: 44 Years
- Healthy Volunteers: f

Study Arms:
- Natural cycles (Type: None): Endometrium will be sampled at the day of LH surge + 7 days.
- Artificial cycles (Type: None): Endometrium will be sampled at the day of P4 + 5 days.

Based on this trial design, predict the completion outcome and termination type (if applicable).