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Staging Blastocyst Morphology
Introduction
Often communication if IVF is troubled by the fact that there is no clarity on the items
used. For any international registration purposes it is important to assess whether
classification and staging systems are comparable. Therefore we present the Voorburg
staging system of the morphological development of blastocysts. This does not however mean
a grading system such as the classification of day two or day three embryo morphology (
amongst others based upon the degree of fragmentation). As such there is no relationship
between class one embryos (the best morphological ‘quality’) on day three and
the staging of blastocysts on day five
Justification: sequence and times of procedures
In order to compare our findings with those of others first it is important to know at
which moment these procedures takes place. Follicle Aspiration (FA) and Oocyte
identification almost invariably takes place in the morning, between 08.00 and 13.00
hours, 34 to 36 hours after the hCG injection. Insemination or ICSI usually takes place in
the afternoon between 14.00 and 17.00 h. For IVF oocytes are not denuded, for ICSI they
are. The inspection of signs of
fertilization (pronucleus- PN- inspection) is performed 16
to 18 hours after insemination or ICSI, the following morning. Assessment of
embryo-morphology on day 2 or day 3 after insemination or ICSI occurs around noon.
Assessment thereafter takes place on day 5, around noon. This is done in order to judge
the speed of development in a
standardized manner. Embryo Transfer (ET) always takes place
in the afternoon. Just before transfer of day 5 embryos these are again inspected in order
to know whether further development or possibly hatching has occurred. We have always
related the staging of the embryo on the same day after insemination, i.e. day 5. We have
not extended the culture to day 6 or day 7 when no cavitation is seen on day 5 to see
whether subsequently blastocyst formation takes place.
Classification
We have classified the embryos on day five into the following stages
Degenerated embryos
Embryos show signs of degeneration: signs of fragmentation. This will be added
Pic
Developmental Arrest
Embryos have not developed further than 8-16 cell stage without signs of fragmentation
pic
Morula/ Compaction stage
Embryos have proceeded to the morula or compaction stage, however without any signs of
cavitation
pic
Cavitating Embryos
A cavity has formed within the embryo. This cavity may be just visible, or it may have
fully developed to an expanding blastocysts. For purpose of classification we have graded
the embryos as follows:
 Stage A: Embryo just cavitating on
day 5
 Stage B: Blastocoel, maximally 50
% of the volume of the embryo with or without the Inner Cell Mass (ICM):
 Stage C: Single blastocoel, most
volume of the embryo with or without the Inner Cell Mass (ICM)
 Stage D: Expanded blastocyst with
or without the Inner Cell Mass (ICM)
ICM: Inner Cell Mass: The Inner Cell Mass is described, whether it is
seen or not and its size and shape.
We feel that by introducing such a classification more homogeneity in terminology can be
created between different
centers that perform transfer of blastocysts.
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