The purpose of this prospective observational cohort study is to evaluate the effect of routine clinical anticoagulant therapy on endometrial receptivity and subsequent pregnancy outcomes in women with infertility. Researchers will utilize an ultrasound multimodal system to systematically assess endometrial parameters, including thickness, morphology, peristalsis, and blood flow indices. The study aims to enroll approximately 300 infertile women aged 20 to 45 years. Participants will be observed and grouped based on whether they receive anticoagulant medications, such as aspirin or heparin sodium, as part of their standard clinical care. The study will track ultrasound-based receptivity indicators and follow up on pregnancy status and outcomes at 45 and 90 days of gestation. This study is purely observational, and all clinical treatment decisions are made independently of the study protocol.

Background and Rationale:

Endometrial receptivity plays a pivotal role in the success of embryo implantation for patients with infertility. Impaired endometrial perfusion is considered a significant contributing factor to implantation failure. In routine clinical practice, anticoagulant therapies, such as low-dose aspirin and low molecular weight heparin (e.g., heparin sodium), are frequently utilized to improve local hemodynamics and endometrial receptivity. However, a systematic, non-invasive, and quantitative evaluation of these therapeutic effects on the endometrium is still required.

Multimodal ultrasound provides a comprehensive, real-time, and non-invasive approach to assessing endometrial dynamics. By integrating conventional 2D ultrasound, 3D ultrasound, and Doppler imaging, this technology can meticulously quantify endometrial parameters, offering valuable predictive insights for clinical pregnancy outcomes.

Study Design and Methodology:

This is a single-center, prospective, observational cohort study. The objective is to evaluate the impact of routine anticoagulant therapy on endometrial receptivity and subsequent pregnancy outcomes in infertile women using an ultrasound multimodal system.

The study plans to enroll approximately 300 eligible infertile women aged 20 to 45 years. Participants will be categorized into two observational cohorts based solely on their routine clinical care plans:

Observation Group: Patients receiving anticoagulant therapy (e.g., aspirin, heparin sodium) in addition to conventional treatment.

Control/Comparison Group: Patients receiving conventional treatment only. Note: The decision to administer anticoagulant therapy is entirely at the discretion of the attending physicians based on clinical indications, independent of this study protocol. This study is strictly observational and involves no protocol-driven interventions.

Data Collection and Assessments:

During the clinically defined window of implantation, all participants will undergo comprehensive multimodal ultrasound examinations. The primary ultrasonographic parameters to be recorded include:

Endometrial thickness and morphological patterns.

Endometrial peristalsis characteristics.

Endometrial and subendometrial blood flow indices, including Vascularization Index (VI), Flow Index (FI), and Vascularization Flow Index (VFI) via 3D power Doppler.

Follow-up and Endpoints:

Following the ultrasound assessments and embryo transfer/conception, participants will be longitudinally followed. The clinical endpoints, specifically the pregnancy status and outcomes, will be rigorously tracked and documented at 45 days and 90 days of gestation. The collected data will be analyzed to determine the correlation between the multimodal ultrasound parameters of endometrial receptivity under anticoagulant therapy and the ultimate pregnancy success rates.

Inclusion Criteria:

• Female patients aged 20 to 45 years.

Clinically diagnosed with infertility and planning to undergo embryo transfer or monitored conception cycles.

Patients who have complete baseline clinical data and are willing to undergo multimodal ultrasound evaluation of endometrial receptivity during the window of implantation.

Voluntarily agreed to participate in this observational study and signed the informed consent form for data collection.

Exclusion Criteria:

• Presence of congenital uterine malformations (e.g., septate uterus, bicornuate uterus, unicornuate uterus) that significantly alter the endometrial cavity.

Presence of untreated severe intrauterine lesions, such as submucosal fibroids, severe intrauterine adhesions, or endometrial polyps that may mechanically interfere with implantation.

Severe underlying systemic diseases, including but not limited to severe liver or kidney dysfunction, or malignant tumors.

Known severe bleeding disorders or strict contraindications to anticoagulant medications (for patients in the routine clinical care setting).

Patients who are unable to cooperate with the transvaginal multimodal ultrasound examination or complete the required follow-up for pregnancy outcomes.

The study population consists of adult female patients, aged 20 to 45 years, who have been clinically diagnosed with infertility. These patients are seeking routine infertility treatments, such as in vitro fertilization (IVF) and embryo transfer or monitored conception cycles, at Tangdu Hospital. The population includes patients who receive standard conventional treatment as well as those who are prescribed adjunctive anticoagulant therapy based on their routine clinical care indications.

De-identified individual participant data (IPD) underlying the results reported in the published article will be shared. Data will be available to researchers who provide a methodologically sound proposal, purely for the purpose of achieving the aims in the approved proposal.

Data will be available beginning 6 months and ending 36 months following article publication.

To gain access, data requestors will need to contact the corresponding author and sign a formal data access agreement.