Inverse correlation between female patient's age and embryonic cavitation rate of human embryos cultured in vitro

Abstract

We examined, retrospectively, the relationship between the age of the female patient undergoing Assisted Reproductive Technology (ART) treatment and the incidence of successful cavitation of that patient's embryos on Day 5 post-Oocyte Retrieval (O/R). Previously-published reports have suggested that there is no detectable correlation between these parameters. However, in many ART centers, only a limited sub-population of patients are selected for treatment using Extended Embryo Culture (EEC) in vitro and often, this sub-population is comprised of relatively ‘young’ female patients and/or those receiving donated oocytes. It is well known that the rate of aneuploidy seen in human embryos cultured in vitro is positively correlated with female patient age, and that morphologically normal-appearing human blastocysts can be composed of a large proportion of aneuploid blastomeres. In our center, patients are normally treated with an Embryo Transfer (ET) procedure performed on Day 5 post-O/R, providing that a minimum of four ‘good quality’ embryos are available on Day 2 post-O/R. Patients who underwent EEC prior to ET, and who were treated using non-donated oocytes and non-cryopreserved embryos, were selected for this study (103 Cycles). For each patient included in the study, the age of the female patient was determined, and the number of embryos exhibiting a detectable blastocoelic cavity, and the number of non-cavitated zygotes/embryos, on Day 5 post-O/R, were determined by microscopy. The data were plotted as an XY scatter plot and the regression equation and the correlation coefficient were calculated and the regression line plotted. Patients were treated using conventional in vitro fertilization and/or Intracytoplasmic Sperm Injection techniques using standard methods. Correlation analysis indicated that there was a significant (P<0.005) negative correlation between the age of the female patient and the incidence of successful cavitation of that patient's embryos on Day 5 post-O/R. Our study demonstrates a significant negative correlation between the age of the female patient and the incidence of successful cavitation of that patient's embryos on Day 5 post-O/R. These findings may provide an indirect indication that ‘advanced maternal age’ is associated with a decrease in the mean embryonic cavitation rate due to a concomitant rise in the incidence of aneuploidy in the constituent blastomeres of the embryo when compared to younger female patients.