Embryo transfer day 2 or day 3: comparison of pregnancy rates of IVF cycles of normal responder patients with few available embryos

Abstract

OBJECTIVE: The aim of this study was to compare pregnancy rates between day 2 and day 3 ET in a population of normal responder women with few available embryos. DESIGN: Retrospective study MATERIALS AND METHODS: We retrospectively analyzed 602 consecutive ET from July 2005 to December 2008. The subjects fulfilled the following criteria: female age < 40 years, more than 4 retrieved oocytes per cycle. All patients underwent similar controlled ovarian hyperstimulation. When 2 or more follicles measured 19mm, retrieval occurred 35 hours post hCG administration. Three (female age < 35 years) or four (female age > 34 years) best retrieved oocytes were selected and were treated with intracytoplasmatic sperm injection or conventional insemination methods. All embryos resulting from the oocytes were transferred without selection. We routinely performed day 2 ET except for constraints of working days. (Biochemical) pregnancy was defined by quantitative hCG > 5 mUI/ml 12 days post transfer. Differences in the means of continuous measurements were tested using the Student t test. A p value of less than 0.05 was considered to indicate statistical significance. RESULTS: 383 cases (64%) were assigned to Day2 ET and 219 cases (36%) to Day3 ET. Female mean age was 33.9 (D2) and 33.4 years (D3). There were no significant differences between the groups regarding the mean ages of males and females, mean number of total retrieved oocytes (9.5 D2 and 9.8 D3), mean number of MII oocytes retrieved (7.2 D2 and 7.4 D3), and total number of embryos transferred (2.9 D2 and 3.0 D3). Day 2 pregnancy rate was 40.3% and day 3 pregnancy rate was 32.8%. The day 2 group had a significantly higher association with pregnancy independently of the ages of males and females, number of inseminated oocytes and total embryos transferred (OR= 1.45, 95%CI= 1.01 to 2.08, p= 0.045). CONCLUSIONS: This data shows no real advantage to culture to day 3 when there are no embryo selection in normal responder women.