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Published on: December 3, 2012
Time-lapse imaging of cytoplasmic strings at the blastocyst stage suggests their association with spontaneous
Thomas Ebner1, Özcan Sesli2, Sanja Kresic1
1Kepler University, Department of Gynecology, Obstetrics, and Gynecological Endocrinology, Krankenhausstrasse 26-30, Linz Upper Austria, Austria.
Research Question:
To study the origin and temporal behaviour of cytoplasmic strings spanning the blastocoel (main objective) and their influence on treatment outcome (secondary objective).
Design:
This retrospective analysis of prospectively collected data was set up in a university medical centre. Patients who either underwent fresh (n = 95) or vitrified-warmed (n = 55) single blastocyst transfer were included. Time-lapse sequences of in-vitro developed blastocysts were screened for the presence of cytoplasmic strings. Pregnancies in string-positive and string-negative transfers were followed up to live birth.
Results:
A total of 387 blastocysts were obtained in the fresh cycles of 100 patients, corresponding to a blastocyst formation rate of 62.4%. Cytoplasmic strings were first detected around full stage (108.5 ± 6.4 h) in 170 blastocysts (43.9%). The number of strings varied (range: 1-7) and the duration of visibility was 5.2 ± 3.5 h. The occurrence of cytoplasmic strings was significantly associated with the presence of blastocoelic collapses (P < 0.001) but not with any of the annotated morphokinetic parameters. Live birth and neonatal outcome were the same for both string-positive and string-negative pregnancies. Moreover, collapses did not affect treatment outcome.
Conclusion:
Time-lapse analysis of cytoplasmic strings at the blastocyst stage revealed that this morphological feature was not a negative predictor as previously reported. Although physiologically normal, at least some of the cytoplasmic strings are an artefact, possibly associated with blastocoelic collapses.
