F. Other morphological features

F.1 Vacuoles/vacuolation

Vacuoles can arise during in vitro culture of human embryos at any stage of development (Ebner et al., 2005). Those first detected on Day 4 of development have the most severe impact on blastocyst development (Ebner et al., 2005). Vacuoles appearing in early development cannot often be detected within the blastocyst or can be detected only in excluded cells (Ebner et al., 2005). Vacuoles when found within the blastocyst appear more often in the TE than in the ICM (Figs 392–394; Ebner et al., 2005). These vacuoles should be distinguished from degenerative changes or vacuolation described and classified as BG3 blastocysts by Dokras et al., 1993.

F.2 More than one point of natural hatching

A rare finding in blastocyst assessment is the occurrence of two or more sites of hatching (Figs 395–397; 2%; Fong et al., 2001). It has been suggested that this might arise in ICSI-generated blastocysts due to incomplete closure of the zona breach created by the microinjection pipette (Fong et al., 1997). Hatching at more than one point in the ZP, particularly when one of the holes is very small could result in trapping of the blastocyst within the ZP as the pressure within the blastocoel cavity would be dissipated and not concentrated on one hatching site.

Article references:

Ebner T, Moser M, Sommergruber M, Gaiswinkler U, Shebl O, Jesacher K, Tews G. Occurrence and developmental consequences of vacuoles throughout preimplantation development. Fertil Steril 2005;83:1635-1640.
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Fong CY, Bongso A, Ng SC, Anandakumar C, Trounson A, Ratnam S. Ongoing normal pregnancy after transfer of zona-free blastocysts: implications for embryo transfer in the human. Hum Reprod 1997;12:557-560.
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Fong CY, Bongso A, Sathananthan H, Ho J, Ng SC. Ultrastructural observations of enzymatically treated human blastocysts: zona-free blastocyst transfer and rescue of blastocysts with hatching difficulties. Hum Reprod 2001;16:540-546.
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Dokras A, Sargent IL, Barlow DH. Human blastocyst grading: an indicator of developmental potential? Hum Reprod 1993;8:2119-2127.
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