Analyzing cervical mucus to identify markers for endometrial receptivity in infertility treatment

Inclusion Criteria - Arm A - stimulated cycle:

* female aged less than 37 years (maximally 36y + 364d)
* no smoker
* normal menstrual cycles lasting between 25 to 35 days
* had been infertile for less than five years
* normal responder
* fewer than three failed cycles of assisted reproduction treatment, including fresh IVF/ intracytoplasmic sperm injection (ICSI) embryo transfer cycles and/or frozen-thawed embryo transfer cycles
* sperm obtained through ejaculation
* spermiogram more than 5 million sperm/mL
* BMI 19-29 kg/m2
* follicle stimulating hormone (FSH) \< 10 IU/L on the third day
* basal antral follicle count of 5-15
* undergoing the same routine gonadotrophin-releasing hormone agonist (GnRHa) long depot or gonadotrophin-releasing hormone antagonist (GnRH-ant.) protocol
* informed consent

Exclusion Criteria - Arm A - stimulated cycle:

* genetic disease
* metabolic and/or endocrine disorders
* polycystic ovary syndrome (defined by the Rotterdam criteria)
* women with prior diagnosis of endometriosis or adenomyosis
* previous gynecological/pelvic surgery except for salpingectomy
* repeated spontaneous abortions (two or more)
* previously less than 5 oocytes and/or serum anti-Mullerian hormone value \< 1.0 mIU/ml or more than 20 oocytes, milli-International unit (mIU)
* previous ovarian hyperstimulation syndrome (OHSS)
* presence of any structural abnormality of the reproductive system
* donor oocyte cycles
* severe male factor infertility \< 5 million sperm/mL
* low response to stimulation
* endometrium \< 8 mm at the day of human chorionic gonadotropin (hCG) or ET
* number of retrieved oocytes 5 - 20
* low fertilization capacity (rate of fertilization \< 20% and late ICSI following IVF fertilization failure)
* OHSS
* IVF cycle cancelled before ET
* other than easy one high-quality blastocyst transfer (at least grade 3BB)

Inclusion criteria - Arm B - substituted cycle:

* female aged less than 37 years (maximally 36y + 364d)
* no smoker
* normal menstrual cycles lasting between 25 to 35 days
* had been infertile for less than five years
* normal responder at stimulation
* fewer than three failed cycles of assisted reproduction treatment, including fresh IVF/ intracytoplasmic sperm injection (ICSI) embryo transfer cycles and/or frozen-thawed embryo transfer cycles
* sperm obtained through ejaculation
* spermiogram more than 5 million sperm/mL
* BMI 19-29 kg/m2
* FSH \< 10 IU/L on the third day
* undergoing the same routine estrogen/progesterone substituted cycle
* informed consent

Exclusion criteria - Arm B - substituted cycle:

* genetic disease
* metabolic and/or endocrine disorders such as diabetes, metabolic syndrome, and thyroid disorders
* polycystic ovary syndrome (defined by the Rotterdam criteria), hyperprolactinaemia
* women with prior diagnosis of endometriosis or adenomyosis
* previous gynecological/pelvic surgery except for salpingectomy
* repeated spontaneous abortions (two or more)
* previously less than 5 oocytes and/or serum anti-Mullerian hormone value \< 0.5 mIU/ml in the stimulated cycle
* previous OHSS
* presence of any structural abnormality of the reproductive system
* severe male factor infertility \< 5 million sperm/mL in the stimulated cycle
* number of retrieved oocytes 5 - 20 in the stimulated cycle
* low fertilization capacity (rate of fertilization \< 20% and late ICSI following IVF fertilization failure)
* endometrium less than 8 mm at the day of thawing and transfer indication
* thawed blastocyst cycle cancelled before ET
* other than easy one best quality frozen/thawed blastocyst transfer (at least grade 3BB)