In Vitro Fertilization (IVF) success is below 40%, with Embryo Transfer the leading cause of IVF failure. This clinical investigation aims to evaluate if the levels of an intrauterine biomarker dissolved in the uterine fluid (alone or as a complex biological marker) can predict the outcome of embryo transfer.

Seedchorny02 is an exploratory study, with blind evaluation by third parties, in a single center and without influencing clinical practice. The goal of this investigation is to evaluate if the levels of an intrauterine biomarker that is dissolved in the endometrial fluid can predict the outcome of embryo transfer, when measured the day before or on the day of embryo transfer.

80 IVF volunteers in a frozen embryo transfer cycle with high-quality day-five blastocysts are expected to be recruited. For intrauterine measurement, the investigational device Seedchrony RUO 02 will be used. Seedchorny RUO 02 has a microsensor integrated into the transfer catheter to measure the biomarker level in the uterine fluid entering the transfer catheter. Other patients' clinical variables and IVF cycle parameters (hormonal levels, ultrasound parameters, embryo quality grades, and transfer protocol) will also be collected.

Primary variable: Relationship between intrauterine dissolved biomarker concentration (alone or as a complex biological marker) and the outcome of the embryo transfer.

Notes: The intrauterine biomarker concentration is measured twice: the day before the transfer and on the transfer day. Complex biological marker refers to combining the concentration of the biomarker on both days and/or with other clinical variables of the patient/embryo.

The outcome of the embryo transfer is evaluated as:

Chemical pregnancy: positive pregnancy test (blood hGC detection); Clinical pregnancy confirmed by ultrasound at week six (detected gestational sac); Ongoing pregnancy at week eight, confirmed by ultrasound at week eight (detected gestational sac and heartbeat).

Inclusion Criteria:

• First IVF cycle patients

• Patients who sign the informed consent form

• Patients between 18 and 37 years old.

• Patients BMI ≤ 30

• Patients who have frozen blastocysts of good quality (grade A or B)

• Patients with negative vaginal and endocervical cultures

• Patients with an antimullerian hormone level greater than 1 ng/mL.

• IVF patients with an endometrial thickness greater than 7mm with trilaminar pattern on the day of the pre-progesterone visit.

• And who meets one of these conditions:

  1. Not having had a previous embryo transfer.
  2. Have failed only one embryo transfer

Exclusion Criteria:

• Patients with seminal data of the couple with severe oligozoospermia (sperm concentration <1 million sperm per ml) or azoospermia (absence of sperm in the ejaculate)
• Patients diagnosed with at least one of the following uterine pathologies: endometriosis, cancer, malformations, untreated polyps, or submucous fibroids.
• Patients diagnosed with at least one of the following medical pathologies: Polycystic ovary syndrome (PCOS), insulin-dependent diabetes mellitus, Cushing's syndrome, uncorrected thyroid dysfunction, hepatic and/or renal insufficiency, a pathology that contraindicates ovarian stimulation and/or gestation, antiphospholipid syndrome, and autoimmune disease.
• Patients who are currently taking any medication other than contraceptive treatments, which may interfere with fertility or menstrual cycle regulation.
• Evidence of drug, tobacco, or alcohol abuse or dependence according to medical history or information provided by the patient.
• Inadequate understanding (oral and written) of the Spanish language.