Preimplantation Genetic Diagnosis (PGD) by Array Comparative Genome Hybridization (CGH) and Blastocyst Biopsy

Overview

This study evaluates the effect of single embryo transfer (SET) with and without array CGH for the evaluation of the complete chromosome complement of the blastocyst. Patients will be allocated at random into two groups. The control group will consist of patients in which one embryo will be replaced on day 5 based on morphological and developmental characteristics, and the other embryos reaching blastocyst stage will be vitrified. The test group will consist of patients undergoing embryo biopsy at the blastocyst stage (day 5 of development, embryo freezing, and analysis of the biopsied cells with a comprehensive chromosome analysis technique (array Comparative Genome hybridization or aCGH). Only a chromosomally normal blastocyst will be replaced in a thawed cycle. Inclusion and exclusion criteria are described in the study population section.

Rational for the study: The goal of this study is to determine if the strategy employed for the Test group can solve two major problems in ART, one the still low implantation rate in women of advanced maternal age, and two the frequent occurrence of multiple pregnancies resulting from solving the first problem by replacing too many embryos. Preimplantation Genetic Diagnosis (PGD) has been proposed as a potential means to achieve these goals, but so far, the results with day 3 biopsy and FISH analysis of 5-12 chromosomes has produced contradictory results, the difference between studies being explained by technical differences (Munne et al. 2010). Three technical developments have recently occurred that can change dramatically the efficacy of PGD. One, blastocyst laser assisted biopsy, which seems less detrimental than cleavage stage biopsy; Two, vitrification of embryos which allows those blastocysts to be frozen with little or no loss of viability, and three, chromosome comprehensive screening techniques, such as array CGH (Gutierrez-Mateo et al. 2011) which allow for the detection of all chromosome abnormalities. Preliminary data from our center indicates that the technique to be used, an improvement on our prior technique CGH, will result in a very significant improvement in implantation rates and a reduction in miscarriage rates, thus justifying the use of single embryo transfer in this set up. Supportive Preliminary Research: In a recent study, the investigators observed a 1.6 fold increase (p \< 0.001) in implantation rate when aCGH was applied to blastocyst embryos (Schoolcraft et al. 2010). The test group used CGH, an older and less sensitive iteration of the technique to be used in the proposed study - array CGH. Array CGH has a 6 megabase resolution and screens for 30% of all DNA bases (compared to 0.1% of SNP arrays). With array CGH the false positive and false negative rate is 0% when biopsying blastocysts, and 3% when biopsying day 3 embryos (Gutierrez Mateo et al, 2011). Based on our preliminary data, patients with 5 or more day 3 embryos and less than 43 years of age are the most likely to benefit from PGD, since they produce enough embryos and enough normal embryos so a selection technique, like PGD could chose them and improve their reproductive odds. Also our PGD preliminary data shows a \< 10% of embryo demise after implantation for a population 38 of age (expected would be about 28%). Study Hypothesis The investigators foresee a significant increase in implantation rates in the Test group compared to the Control group. The investigators calculated that 60 patients in each arm would be needed to achieve a significant increase in implantation rates (p \< 0.05) with a power of 80%, based on a comparative study in which the investigators observed a 1.6 fold increase in implantation rate (Schoolcraft et al. 2010). Study population, interventions: see below.