STUDY QUESTION<\/p>\n
Are the fetal outcomes of singleton pregnancies that result from cleavage stage embryo transfer (ET) different from the outcomes from Day 5\/6 blastocyst stage ET?<\/p>\n
SUMMARY ANSWER<\/p>\n
There was a significantly higher risk of preterm birth (<37 weeks) in singletons after extended embryo culture (Day 5\/6) compared with cleavage stage (Day 3) transfer.<\/p>\n
WHAT IS KNOWN ALREADY<\/p>\n
Two recent studies, from Sweden and the USA, reported an increased risk of preterm birth in singleton pregnancies after Day 5\/6 ET compared with Day 3 ET. The US study also showed increased early preterm births and the Swedish study showed increased fetal malformations in this group.<\/p>\n
STUDY DESIGN, SIZE AND DURATION<\/p>\n
A retrospective cohort study was performed. Data were collected from the Canadian ART Register database for all singleton births after fresh IVF\/ICSI ET cycles (2001–2009).<\/p>\n
PARTICIPANTS\/MATERIALS, SETTING, METHODS<\/p>\n
A total of 12 712 singleton births were included. Of these, 9506 resulted from a Day 3 ET and 3206 resulted from a blastocyst (Day 5\/6) ET.<\/p>\n
MAIN RESULTS AND THE ROLE OF CHANCE<\/p>\n
Preterm birth rate <37 weeks (unadjusted by potential confounding factors) was higher with Day 5\/6 versus Day 3 transfers (17.2 versus 14.1%, P<\/I> < 0.001). Using logistic regression analysis to adjust for confounding factors, preterm birth rate <37 weeks was the only outcome significantly increased after Day 5\/6 compared with Day 3 transfer (odds ratio 1.32, 95% confidence interval 1.17–1.49). The following confounding factors were adjusted for: year of treatment (2001–2009), maternal age (continuous), parity (0 versus ≥1 birth), diagnosis category, number of oocytes retrieved [≤20 versus >20 (high responder group)], insemination method (IVF versus ICSI), number of embryos transferred (1, 2 or ≥3) and the presence of a vanishing twin (≥1 fetal heart on the initial ultrasonographic examination).<\/p>\n
LIMITATIONS, REASONS FOR CAUTION<\/p>\n
Post-natal follow-up studies will be required to determine if this difference we observed translates into adverse long-term effects on these offspring. The rate of early preterm births (<32 weeks) was higher in Day 5\/6 versus Day 3, but the low number of cases in this category did not have the power to show a difference (3.0 versus 2.7%, P<\/I> = 0.34).<\/p>\n
WIDER IMPLICATIONS OF THE FINDINGS<\/p>\n
We found a significantly higher risk of preterm birth (<37 weeks) in singletons after extended embryo culture (Day 5\/6) compared with cleavage stage (Day 3) transfer, even when adjusting for confounding factors. Our findings are in agreement with the previous two studies; however, we did not show a difference in the very preterm deliveries (unlike the US study) or in fetal malformations (as in the Swedish study). We hypothesize that there may be a deleterious effect of prolonged in vitro<\/I> embryo culture on subsequent placentation. Longer term follow-up studies will be required to determine if prolonged in vitro<\/I> culture to the blastocyst stage has an adverse effect on the long-term health of offspring when compared with shorter cleavage stage culture.<\/p>\n
STUDY FUNDING\/COMPETING INTEREST(S)<\/p>\n
None.<\/p>\n
Source: STUDY QUESTION Are the fetal outcomes of singleton pregnancies that result from cleavage stage embryo transfer (ET) different from the outcomes from Day 5\/6 blastocyst stage ET? SUMMARY ANSWER There was a significantly higher risk of preterm birth (<37 weeks) … Continue reading
http:\/\/humrep.oxfordjournals.org\/cgi\/content\/short\/28\/4\/924?rss=1<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"