Randomized sibling-oocyte study comparing high-magnification imsi versus conventional ICSI: does it influence embryo development?

A. De Vos, Hilde Van De Velde, Geertrui Bocken, Nadine Franceus, Griet Meersdom, Sara Tistaert, Heidi Van Ranst, Paul Devroey, Greta Verheyen

Research output: Contribution to journalConference paper


Introduction: The use of high magnification for morphological sperm selection
prior to ICSI has been associated with higher pregnancy rates and lower
miscarriage rates. The presence of nuclear vacuoles in the sperm head seems
to influence embryo development. In order to further explore the influence of
morphological sperm selection on embryo development, a prospective sibling
oocyte study was started.
Material and Methods: Between March and December 2010, 182 couples
(190 cycles) planned for ICSI treatment for male factor indication and in their
first to fourth attempt were included in the study. For each cycle included, on
the day of treatment, a high-magnification semen morphology was assessed on
at least 200 spermatozoa according to the criteria published by Vanderzwalmen
et al. (2008): grade I, absence of vacuoles; grade II, maximum of two small
vacuoles; grade III, more than two small vacuoles or at least one large vacuole;
grade IV, large vacuoles in conjunction with abnormal head shapes or other abnormalities.
Half of the oocytes of each patient were injected with spermatozoa
selected at higher magnification (1000x), whereas the other half was injected
with conventionally-selected spermatozoa (400x). Primary endpoints were fertilization
rate and embryo development. The clinical outcome remains descriptive
because embryo transfers were not randomized in order not to disfavour the
patient. The embryologist selecting the embryos for transfer was blinded for the
sperm selection procedure used.
Results: All but six semen samples (due to concentration constraints) (n = 184)
allowed to assess the IMSI morphology, resulting in the following distribution:
16.1 ± 13.6% grade I, 11.8 ± 8.7% grade II, 13.9 ± 9.5% grade III and
58.2 ± 22.6% grade IV. In total, 1586 oocytes were injected, showing a fertilization
rate of 81.9% and 79.7% after IMSI and ICSI respectively (NS, paired
t-test). Over 98% of the IMSI-oocytes were injected with grade I (89.0%) or
grade II (9.3%) spermatozoa. The IMSI fertilization rate per oocyte injected
was 81.0% with grade I spermatozoa and 71.2% with grade II spermatozoa.
Embryo development was similar for the IMSI and the ICSI treatment groups
up to day 5 of preimplantation development. Five cycles remained without
embryo transfer (due to insufficient embryo quality (n = 4) or for medical reason
(n = 1)) and 42 transfers included embryos from both IMSI and ICSI treatment
and thus were not informative. Comparable numbers of IMSI (n = 68) and
ICSI (n = 75) embryo transfers were performed. Clinical pregnancies with fetal
heart beat were equally distributed over transfers with embryos from only IMSI
(34.8%) or only ICSI treatment (35.4%).
Conclusions: The present study did not show a difference in fertilization rate
nor in embryo development between high-magnification IMSI and conventional
ICSI. The clinical outcome was similar for IMSI and conventional ICSI.
More treatment cycles are needed in order to reach an adequate power and in
order to define a possible target population (severity of the male factor, rank of
attempt) that might benefit from the IMSI approach.
Original languageEnglish
Pages (from-to)73
Number of pages1
JournalHuman Reproduction
Publication statusPublished - Jul 2011
EventUnknown -
Duration: 1 Jul 2011 → …


  • sibling oocyte


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