Patient case (clinical description): A 32-year-old woman comes to the hospital with vaginal spotting.  Her last menstrual period was 10 weeks ago. She has regular menses lasting for 6 days and repeating every 29 days. Medical history is significant for appendectomy and several complicated UTIs. She has multiple male partners, and she is inconsistent with using barrier contraceptives. Vital signs are normal.  Serum β-hCG level is 1800 mIU/mL, and a repeat level after 2 days shows an abnormal rise to 2100 mIU/mL.  Pelvic ultrasound reveals a thin endometrium with no gestational sac in the uterus.

Patient's own account: I just turned 32 and last morning I woke up with strange blood stains on my underwear. My last periods were more than 2 months ago, which is unusual for me because I used to have regular periods lasting for 6 days every 29 days, more or less. I had several UTIs in the past. I also had appendicitis. I'm currently seeing several men and, to be honest, some of them do struggle to wear a condom. I went to the hospital to check myself up and they told me that my vitals were normal. I also had a blood test on Monday, and my β-hCG level was 1800 mIU/mL, and then on Wednesday, it went up to 2100 mIU/mL. The gynecologist also did an ultrasound and she told me that, hopefully, there was no ovule.

Clinical trial: Biomarkers of Endometrial Receptivity

Eligibility criteria:
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)
Female
No healthy subjects accepted to join the trial.

Subject must be at most 36 Years

Eligibility (NLI label): Contradiction