Context. Endometriosis it’s associated with infertility, so assisted reproduction is needed. Not all the ovarian stimulation protocols have shown good results in severe cases. Some pre-hormone therapy and stimulation have been suggested for these patients, but there are no standard protocols. Literature has shown the beneficial of a conservative surgery, but there is no standard consensus. Objective. To find out if it's possible to use a standard protocol to achieve a pregnancy in severe cases of endometriosis in patients undergoing IVF treatment. Methods. Pre-treatment with dienogest for two months in IVF patients with severe and recurrent endometriosis. Stimulation with GnrH agonist and hMG. Decision about surgery in each case. Participant(s). Five <40 years old women with G-IV endometriosis planning IVF were included. Intervention(s). We used a long-term protocol with GnrH agonist for pituitary suppression and hMG for ovarian stimulation. Triggering with r-hCG. Four patients needed a surgery due to the severity of endometriosis according ESRHE guidelines. Main Outcome Measure(s). Age of the patient, previous history, Ca 125 marker, AMH value, number of obtained oocytes, number of embryos and its quality, day of ET and if they got a pregnancy or not. was measured in different times to study endometriosis residual activity. Result(s). A media of 5,7 oocytes, 5MII, 4 embryos were obtained per patient. Number of embryo transferred was 2 (D3) in 3 patients and 1 (D5) in 2. Only one patient had supernumerary blastocysts to freeze. Four single pregnancies, with already 3 new-born healthy children and an ongoing 35th week pregnancy were achieved. The fifth patient got biochemical abortion and now she’s waiting for endometrial preparation to perform an embryo-cryotransfer. Conclusions With our results, we can suggest the need of pre-cycle medical treatment with dienogest as an efficient treatment option for patients with severe endometriosis undergoing IVF. Gonadotropin-releasing hormone analogues with stimulation with 300UI/day of hMG, had shown to be efficient to get an ideal number of quality embryos to be transferred to achieve a pregnancy. Surgery before IVF in G-IV cases of endometriosis has to be determined according to each individual case. If our results are replicated in new patients, we could standardize this treatment protocol in patients with the same characteristics, avoiding the option of donor oocytes as their unique option to get a pregnancy.