INCREASED AGE AND BODY MASS INDEX RELATES TO INCREASED TIME-LAPSE VARIABILITY AMONG EMBRYOS FROM THE SAME CYCLE

Abstract

The negative effect of the increased age and obesity on women’s fertility, natural conception and assisted reproduction is already well known. To date, it is still not fully clear how these important factors could influence different aspects of embryo development and morphokinetics. The aim of the present study was to assess the association between the inter-embryo variability of morphokinetic parameters and patient age and body mass index (BMI). A total of 305 women (967 embryos) were included for analysis in this study. All embryos were cultured in a single culture medium (Life Global, Brussels, Belgium) and a time-lapse system (EmbryoScope, Vitrolife, Sweden). Only women with more than 2 embryos per cycle were included in this study. Fifteen morphokinetic parameters were analyzed: time of pronuclei appearance (tPNa), time of pronuclei fading (tPNf), cleavage times (t2, t3, t4, t5, t6, t7, t8, t9), morulae formation time (tM), starting blastulation (tSB), full blastocyst stage (tB), expansion (tEB) and hatching timing (tHB). Statistical analysis was performed using IBM SPSS Software v.21. Inter-embryo variability for each woman/cycle was measured as the coefficient of variation (CV). Spearman correlation analysis was done to find the association between the coefficients of variation of morphokinetic variables per cycle and female age and BMI. Women age showed low but significant positive correlation with the inter-embryo variability (CV) of certain morphokinetic variables – t7 (r=0.17, p=0.006), t8 (r=0.22, p=0.006), t9 (r=0.13, p=0.048), tB (r=0.18, p=0.022). Moreover, BMI also showed low but significant positive correlation with relatively higher number of CV of time-lapse variables, including earlier events – t3 (r=0.20, p=0.038), t4 (r=0.25, p=0.012), t5 (r=0.24, p=0.02), t6 (r=0.26, p=0.012), t8 (r=0.23, p=0.03) and t9 (r=0.23, p=0.045). In conclusion, time-lapse variability of human embryos is associated with women age and BMI. Embryo morphokinetics variability differs in the initial stages of embryo development according to BMI and in the later stages according to female age.