It is generally assumed that the major causes of in vitro fertilization (IVF) failure in women with endometriosis are diminished ovarian reserve, impaired endometrial receptivity and low quality of embryos. The use of prolonged courses of hormone therapy may play an important role in the strategy of overcoming endometriosis-related infertility. The aim of this study was to evaluate the use of dienogest (DNG) before an IVF cycle in women with endometriosis undergone a previous IVF failed cycle

The primary outcomes of the study are clinical pregnancy rate and live birth rate after reaching 24 week's gestation.

Secondary outcomes of the study are: changes in the diameter and volume of the largest endometrioma, total gonadotropin dose administered, number of mature oocytes collected, number of two-pronuclear (2PN) embryos, number of blastocysts.

Inclusion Criteria:

• diagnosis of endometriosis at magnetic resonance imaging or transvaginal ultrasonography;
• one failed previous IVF cycle (including failure of frozen embryo transfer);
• basal FSH < 14.0 IU/L;
• antimullerian hormone (AMH) blood level >= 0.5 g/mL;
• normal thyroid-stimulating hormone and prolactin.

Exclusion Criteria:

• history of surgery for endometriosis;
• history of uterine or adnexal surgery;
• use of hormonal therapies for the treatment of endometriosis related pain within 6 months before IVF;
• adenomyosis (magnetic resonance imaging or transvaginal ultrasonography);
• hydrosalpinx;
• submucosal fibroids;
• body mass index (BMI) ≥ 30 kg/m2;
• severe male factor infertility (< 5 million total motile sperm count).

Patients with endometriosis who previously failed one IVF cycle and all resultant frozen embryo transfer