ORIGINAL ARTICLE/ÖZGÜN ARAŞTIRMA 77 Introduction Controlled ovarian stimulation in assisted reproductive technologies (ART) induces multiple follicular recruitment and allows the harvesting of multiple oocytes to obtain embryos. During initial studies with human menopausal gonadotropin (HMG) stimulation of multiple follicle development for in vitro fertilizing (IVF), a premature luteinizing hormone (LH) peak occurred in around 20–25% of the cycles. This advanced exposure to high LH resulted in the premature luteinization of follicles and the induction of oocyte maturation, resulting in either cycle cancellation or compromised IVF outcome. The most widely used protocol for ovarian stimulation in ART cycles is the long down- regulation protocol, for which gonadotropins are administered after pituitary suppression with gonadotropin- releasing hormone (GnRH) agonists. With the clinical development of GnRH agonists in the early 1980s, there was not only the increase in pregnancy and live-birth rates, but also a more fexible timing for oocyte retrieval became possible in IVF treatments [1]. The effect of prolonged time for achieving ovarian suppression before starting stimulation on pregnancy rates in ART cycles ART sikluslarında stimulasyona başlamadan önce uzamış ovaryen süpresyonun gebelik oranlarına etkisi Tevfk YOLDEMİR ABSTRACT Objective: To determine if the prolonged time for achieving ovarian suppression before starting stimulation affected the pregnancy rates. Patients and Methods: Retrospective cohort analysis was performed on 565 women undergoing frst assisted reproductive technologies (ART) treatment in a University-affliated Hospital. The women were grouped according to the duration of down- regulation by gonadotropin-releasing hormone (GnRH) analogue. Group A consisted of women in the lower 25th percentile, group B consisted of women in the upper 25th percentile, according to the duration of GnRH analogue use. The implantation and clinical pregnancy rates were compared. Results: Mean number of aspirated and inseminated oocytes were more in group A than in group B. Implantation rates were similar. Clinical pregnancy rates were alike. Conclusion: Prolonged time for achieving ovarian supression does not compromise clinical pregnancy rates in ART cycles. Key words: GnRHa, ART, Ovarian suppression, Pregnancy, Extended protocol ÖZET Amaç: Stimulasyona başlamadan önce ovaryen süpresyonun uzamasının gebelik oranlarına etkisini araştırmak Hastalar ve Yöntem: Üniversite affliye hastanede yardımcı üreme tetkikleri (assisted reproductive technologies (ART)) tedavileri yapılan 565 hasta retrospektif olarak incelendi. Kadınlar gonadotropin salgılayan hormon (gonadotropin releasing hormone (GnRH)) analogu ile ovaryen süpresyon süresine göre gruplandırıldı. GnRH analog kullanım süresine göre grup A alt 25 persentil içinde, grup B de üst 25 persentil içindeki hastalardan oluşmaktaydı. İmplantasyon ve klinik gebelik oranları karşılaştırıldı. Bulgular: Grup A’da ortalama aspire edilen ve insemine edilen oosit sayısı grup B’dekinden fazla idi. İmplantasyon oranları benzer idi. Klinik gebelik oranları benzer idi. Sonuçlar: Ovaryen süpresyon için geçen zamanın uzaması ART sikluslarında klinik gebelik oranlarını olumsuz etkilemez. Anahtar kelimeler: GnRH, ART, Ovaryen süpresyon, Gebelik, Uzun protokol Tevfk Yoldemir (  ) Department of Obstetrics and Gynecology, School of Medicine, Marmara University, Istanbul, Turkey e-mail: dr_yoldemir@hotmail.com Submitted/Gönderilme: 03.03.2013 - Accepted/Kabul: 07.04.2013 Marmara Medical Journal 2013; 26:77-81 DOI:105472/MMJ.2013.02650.1