In a prospective cohort study investigators will examine characteristics and clinical outcomes of treatment with ART in women with tubal factor infertility (TFI) with regard to seropositivity to antichlamydial antibodies.

At the first day of stimulation blood analyses for immunoglobulin G (IgG), immunoglobulin A (IgA) and immunoglobulin M (IgM) to major chlamydial antigens (anti-C.trachomatis), major outer membrane protein (MOMP) and plasmid-encoded protein (pgp3) will be performed for patients found eligible for the study.

According to the result of chlamydial antibody test (CAT) participants will be divided into two groups: group A - women with at least one of antibodies detected (CAT+); Group B - seronegative subjects (CAT-).

Women of both groups will undergo a conventional ovarian stimulation (COS) with GnRH antagonist and daily gonadotropin administration at the dose of 150-300 international unit (IU).

Retrieved oocytes following fertilization (conventional IVF or ICSI) will be cultured to Day 3-5 in vitro; ultrasound guided single or double embryo transfer will be performed; remaining embryos of eligible quality will be vitrified.

Patients will be followed up to live birth. Frozen/thawed embryo transfers (FET) will be performed until at least one live birth (≥20 weeks of gestation) occurred or all embryos resulting from the mentioned assisted ovarian stimulation were used.

Inclusion Criteria:

• Tubal factor infertility diagnosed by laparoscopy;
• Female age between 20-41 years;
• BMI 17,5-35 kg/m2;
• Early follicular phase follicle stimulating hormone (FSH) ≤15 IU/L
• Presence of viable spermatozoa in partner's sperm;
• Signed informed consent.

Exclusion Criteria:

• previous ovarian surgery;
• endometriosis;
• antimullerian hormone (AMH) level ≤0,3 ng/ml;
• hyper- or hypogonadotropic ovarian failure;
• severe male factor infertility;
• Pre-existing medical condition preventing or interfering with IVF treatment: any clinically significant systemic disease; inherited or acquires thrombophilia and thromboembolism; endocrine or metabolic abnormalities; moderate or severe impairment of renal or hepatic function; any oncological diseases in anamnesis; known history of recurrent miscarriage, abnormal karyotype of both partners; currently active pelvic inflammatory disease;
• Abnormal IVF screening tests: Papanicolaou (PAP) smear, Syphilis, HIV 1&2, Hepatitis B, Hepatitis C, Chlamydia, and Gonorrhea;
• Presence of uterine pathology: Asherman's Syndrome, endometrial polyps, nodus form of adenomyosis or uterine fibroids ≥3 mm in diameter;
• Visualization of ovarian cysts ≥25 mm, endometriomas or hydrosalpinx;
• One or more follicles ≥8 mm at the start of the COS protocol.

at the end of recruitment ICF and brief CRF will be shared. At the study completion - CSR and SAP will be uploaded

at the study completion for 1 year

30 random CRFs will be shared, more by request