Prognostic value of growth of 4-cell embryos on the day of transfer in fresh IVF-ET cycles

Purpose To investigate the prognostic value of growth of 4- cell embryos on the day of transfer in determining clinical pregnancy and live birth rates after fresh in vitro fertilization (IVF)-embryo transfer (ET) cycles. Methods Retrospective cohort study of all patients between January 2008 and January 2013 initiating fresh IVF-ETcycles resulting in embryos that were not more than 4 cells 72 h after oocyte retrieval in the morning of their transfer. Patients were stratified into 2 groups based on whether embryos did or did not grow more than the 4-cell stage on the afternoon of ET. The odds of clinical pregnancy and live birth were considered as primary outcomes. Student’s t-tests and Chi-square (χ2) tests were used as inidicated, with logistic regression controlling for maternal age and number of embryos transferred. Results Three hundred forty three patients were identified for inclusion: 165 and 178 patients had 4-cell embryos with and without growth on the afternoon of ET, respectively. The demographic and baseline IVF cycle characteristics of the study cohort were comparable. Patients with embryo growth had higher clinical pregnancy (13.9% vs. 4.49%) and live birth (10.9% vs. 3.37%) rates compared to patients without embryo growth. This represented an overall increased odds of clinical pregnancy [Odds ratio (OR)=3.44; 95% Confidence Intervals (CI) 1.49–7.93; P=0.004)] and live birth (OR=3.51; 95% CI 1.36–9.07; P=0.01). The increased odds remained unchanged after adjusting for maternal age and number of embryos transferred. Conclusions Transfer of 4-cell embryos 3 days after oocyte retrieval can result in clinical pregnancies and live births, albeit at a low rate. Growth of an embryo more than the 4-cell stage on the afternoon of ET may serve as a positive prognostic factor for IVF-ET cycle outcome.