使用time-lapse即時觀測囊胚ICM數量預測單絨毛膜雙羊膜同卵雙生

囊胚期植入同卵雙胞胎比例較高,
使用time-lapse即時觀測胚胎可偵測囊胚之ICM數量，
若有2 ICM之囊胚植入後可能行成囊胚monochorionic/diamniotic----最常見之單絨毛膜雙羊膜之同卵雙生

http://humrep.oxfordjournals.org/content/22/suppl_1/i9.full.pdf+html?ijkey=585c21253b2644a26b17a7d5cd20dfe24c87f97f&keytype2=tf_ipsecsha


O-022 Oral Time-lapse recording identifies human blastocysts at
risk of producing monzygotic twins
D. Payne1
, A. Okuda1
, Y. Wakatsuki1
, C. Takeshita1
, K. Iwata1
, T. Shimura1
,
K. Yumoto1
, Y. Ueno1
, S. Flaherty1
, Y. Mio1
1
Mio Fertility Clinic, Reproductive Centre, Yonago, Japan
Introduction: Monozygotic twinning (MZT) has three aetiologies: dichorionic, in which two blastocysts arise from one zygoyte; monochorionic/diamniotic, the most common, in which two inner cell masses (ICM) form prior to
hatching; and monochorionic/monoamniotic in which the embryonic disc separates at day 8–12. The in vivo frequency is 3 per thousand deliveries (Tuchmann-Duplessis et al, 1971). Much higher MZT frequencies have been reported
after transfer of in vitro derived blastocysts (Wright et al, 2004), which not only
creates perinatal issues but also lessens the efficacy of single blastocyst transfer.
This elevated frequency is thought by some to result from abnormal hatching in
which the embryo is split through the ICM, forming two blastocysts and thus,
dichorionic MZT (Da Costa et al, 2001). Since data on the chorionicity of MZT
are scarce and embryo splitting seemed unlikely, we undertook a time-lapse
study of blastocyst formation to determine possible causes of in vitro derived
MZT.
Materials and methods: Surplus frozen-thawed IVF (n¼21) and ICSI (n¼13)
embryos were donated to this study. Most were frozen at 2–10 cells, some at
morula (n¼7). All but one survived with .50% blastomeres intact. Embryos
were maintained at 37ºC in 5% CO2 in an environmental chamber for up to
5 days and images were recorded digitally every 2 minutes using MetaMorph
(Molecular Devices, USA). Recording commenced immediately after thawing.
Results: The blastocoel cavity formed in 26/33 (79%) of embryos and 17/33
(52%) formed fully expanded blastocysts. Eleven of the 17 (65%) blastocysts
herniated through the zona pellucida and 6 (35%) hatched completely. There
was no evidence of embryo splitting during hatching. Intermittent blastocoel
collapse was common, and 25/26 (96%) of blastocysts had at least one collapse. The frequency and degree of collapse varied, but embryo mortality
was associated with more frequent and higher amplitude collapses. Fifteen of
33 embryos (45%) degenerated during culture and of these, 11 (73%) did not
re-expand after a collapse and subsequently degenerated. One expanded blastocyst (4%) had no ICM, 22/26 (85%) had one ICM and most significantly,
2/26 (8%) had two distinct ICM’s. A third embryo had an equivocal second
ICM. The second ICM was evident early in blastocyst formation in both
embryos, and appeared to be the result of ectopic adhesion of ICM cells on
the abembryonic trophectoderm wall, seeded during an early collapse of the
blastocyst. Both of these blastocysts hatched completely.
Conclusions: Blastocyst collapse in vitro, often called “contraction”, has been
described in many species (Nimura, 2003) and is thought to be a normal feature
of blastocyst development. However, our findings that collapse was associated
with degeneration of blastocysts as well as the formation of a second ICM,
suggest that these episodes in which blastocoel volume cannot be maintained
may be an artefact of culture, Furthermore, our findings suggest that the formation of two ICM during blastocyst development may be the cause of the
high MZT rate after extended culture. This hypothesis fits well with the long
established aetiology of the most common form of MZT in vivo. Those
embryos at risk of twinning could be easily identified by counting the
number of ICM’s, and the patient appropriately advised. Careful recording of
chorionicity/amnioticity of MZT’s at birth will further clarify embryonic
status after long term culture.