Does coasting in assisted reproductive technology (ART) cycles affect the number of embryos available for blastocyst cryopreservation?

Abstract

To evaluate the affect of coasting on the total number of embryos available for cryopreservation in women undergoing ART. Retrospective cohort study. 558 in vitro fertilization (IVF) / intracytoplasmic sperm injection (ICSI) cycles were reviewed. Of these, 74 patients were coasted for 1-5 days during their stimulation. All embryos were cryopreserved at the blastocyst stage. Only embryos determined to be high-grade by an embryologist were cryopreserved. The percentage of embryos cryopreserved (number of blastocysts cryopreserved / number of oocytes fertilized) were compared between coasted and non-coasted patients. A regression analysis was done to control for maternal age, day 3 follicle-stimulating hormone (FSH), stimulation protocol, fertilization with ICSI and transfer day. Secondary variables evaluated were clinical pregnancy rate (CPR), percentage of mature oocytes, and spontaneous abortion rate (SAB). Means were compared using a logistic model for binary outcomes and analysis of variance for continuous outcomes. Unadjusted means of the percentage of embryos cryopreserved were significantly different between the two groups. Coasting was associated with a higher percentage of embryos cryopreserved (14.2% vs. 8.3%, p < 0.05). However, when controlling for covariates no significant difference existed in the percentage of embryos cryopreserved between patients who were coasted and controls (9.5% vs. 10.3%). There was also no significant difference seen in CPR (38.5% vs. 31.6%), percent of mature oocytes (82.4% vs. 82.6%) or SAB rate (12.5% vs. 10.4%) respectively. Coasting can be done to prevent ovarian hyperstimulation syndrome without compromising the quality of the embryo or pregnancy outcomes.