Outcomes of singleton births after blastocyst versus nonblastocyst transfer in assisted reproductive technology

Prevalence, consequence, and significance of reverse cleavage by human embryos viewed with the use of the Embryoscope time-lapse video system

“…One strategy to achieve this is to extend the culture period and see which embryos reach the developmental milestone of a blastocyst (7). However, despite the apparent health of babies born after the transfer of blastocysts (8,9), concerns exist about the obstetrical, perinatal, and later outcomes of offspring conceived from embryos grown in an extended in vitro culture system (10)(11)(12)(13), resulting in a call for the improved identification of early-cleavage embryos destined to become blastocysts (12). Time-lapse videography has been proposed for doing this (14).…”

Risk of preterm birth after blastocyst embryo transfer: a large population study using contemporary registry data from Australia and New Zealand

“…The mechanism for the higher rate of preterm birth is hypothesized to relate to genetic or epigenetic effects on the trophectoderm cells due to extended culture, resulting in abnormal implantation and placentation (10). Other smaller studies have reported no increased risk of adverse perinatal outcomes after blastocyst transfer compared with cleavage-stage ET (13,14). An Australian study using the Australian and New Zealand Assisted Reproduction Database (ANZARD) found lower rates of preterm birth (20.4% vs. 25.1%) and low birth weight (LBW) (15.7% vs. 20.2%) for babies conceived after blastocyst transfer compared with those conceived after cleavage-stage ET.…”

“…However, this study did not adjust for potential confounding factors and used ART treatment from 2002-2006 (15). A recent meta-analysis that included data from four of the studies previously described (10)(11)(12)(13) concluded that the risk of preterm birth in singletons was significantly higher after blastocyst culture (adjusted OR [AOR] 1.32, 95% CI 1.19-1.46) (16).…”

What are the risks of the assisted reproductive technologies (ART) and how can they be minimized?

“…Could it be that these increased risks are due, as animal data to be discussed later suggest, to imprinting abnormalities resulting from prolonged culture? However, it should be noted that, in contrast, Australian investigators found no statistically significant differences in a retrospective cohort study between transfers on days 5 and 6 (blastocyst) and days 2 and 4 (cleavage-stage) for all maternal and perinatal outcomes [22].…”