Related Experiment Video
Updated: Aug 6, 2026
Physical Manipulation to Generate Xenopus Mini Embryos
Published on: April 10, 2026
A preliminary time-lapse morphokinetic framework to stratify developmental competence in three-pronuclear zygotes on
Hayato Asama1, Junko Otsuki2, Keiko Takahashi3
1Kanazawa Tamago Clinic, Kanazawa, Ishikawa, Japan.
Objective:
To develop a noninvasive, time-lapse imaging-based approach to stratify three-pronuclear zygotes by developmental competence and to identify embryos with higher potential for good-quality blastocyst development and live birth.
Design:
Retrospective observational study.
Subjects:
Zygotes exhibiting three pronuclei after intracytoplasmic sperm injection, collected from three fertility clinics.
Exposure:
Time-lapse imaging assessment of second polar body (PB2) extrusion and quantitative measurement of pronuclear volumes.
Main Outcome Measures:
Discriminative performance of the ratio of combined female pronuclear volume to male pronuclear volume for classifying three-pronuclear zygotes on the basis of PB2 extrusion status (operational definition); blastocyst formation and good-quality blastocyst formation (≥3BB); and supportive posttransfer clinical outcomes (where available).
Results:
A total of 222 three-pronuclear zygotes were analyzed, including 173 operationally classified as putative diploid and 49 as putative triploid according to PB2 extrusion status. The ratio of combined female to male pronuclear volume demonstrated strong discrimination between the PB2-extruded and PB2 extrusion-failed categories (area under the curve, 0.863), with a candidate cut-off of 1.189 yielding high sensitivity and specificity. The overall blastocyst formation rate was 40.1% (69/172) in the PB2-extruded and 32.7% (16/49) in the extrusion-failed group. The good-quality blastocyst formation rate was 23.3% (40/172) in the PB2-extruded and 10.2% (5/49) in the extrusion-failed group. After adjustment for maternal age, PB2 extrusion-based classification was not significantly associated with overall blastocyst formation (adjusted odds ratio [aOR], 1.44; 95% confidence interval [CI]: 0.73-2.86) but remained associated with higher odds of good-quality blastocyst formation (aOR, 2.82; 95% CI: 1.03-7.71). Posttransfer live birth outcomes were available for a subset of transferred embryos under site-specific transfer policies; seven live births were observed, and all live birth cases had volume ratios within 0.61-0.83.
Conclusion:
A time-lapse imaging-based framework integrating PB2 extrusion and pronuclear volumetrics feasibly provides a clinically actionable, noninvasive method to stratify three-pronuclear zygotes by developmental competence and may aid selection of embryos with developmental potential when genetic testing is unavailable or undesirable.
