Systematic review: - Cochrane review (2007) was done to determine if blastocyst stage ETs affect live birth rate and associated outcomes compared with cleavage stage ETs and to investigate what factors may influence this. Of the 50 trials that were identified, 18 randomized controlled trials (RCTs) met the inclusion criteria and were reviewed.
Evidence of a significant difference in live-birth rate per couple between the two treatment groups was detected in favour of blastocyst culture (9RCTs; OR1.35,95% CI 1.05 to 1.74 (Day 2/3:29.4% versus Day 5/6: 36.0%)). This was particularly for trials with good prognosis patients, equal number of embryos transferred (including single embryo transfer) and those in which the randomization took place on Day 3. Rates of embryo freezing per couple was significantly higher in Day 2 to 3transfers (9 RCTs: OR 0.45, 95% CI 0.36 to 0.56). Failure to transfer any embryos per couple was significantly higher in the Day 5 to 6 (16 RCTs; OR 2.85, 95% CI 1.97 to 4.11 (Day 2/3: 2.8% versus Day 5/6: 8.9%)) but was not significantly different for good prognosis patients (9RCTs; OR1.50,95% CI 0.79 to 2.84).
This view provides evidence that there is a significant difference in pregnancy and live birth rates in favour of blastocyst transfer with good prognosis patients with high numbers of eight-cell embryos on Day 3 being the most favoured in subgroup for whom there is no difference in cycle cancellation.