In vitro development and chromosome constitution of embryos derived from monopronucleated zygotes after intracytoplasmic sperm injection

Capsule:
All human embryos derived from monopronucleated zygotes after intracytoplasmic sperm injection are chromosomally abnormal and should be discarded for reproductive purposes.

Authors:
Sílvia Mateo, M.Sc., Mònica Parriego, M.Sc., Montserrat Boada, Ph.D., Francesca Vidal, Ph.D., Buenaventura Coroleu, M.D., Anna Veiga, Ph.D.

Volume 99, Issue 3, Pages 897-902.e1, 1 March 2013

Abstract:

Objective:
To study the chromosome constitution and in vitro development of embryos derived from monopronucleated (1PN) zygotes after intracytoplasmic sperm injection (ICSI).

Design:
Prospective study.

Setting(s):
Private assisted reproduction center.

Material:
Fifty-four 1PN 2PB zygotes obtained from 48 ICSI cycles.

Intervention(s):
Pronuclear diameter was measured 18±2h after ICSI and embryonic in vitro development was assessed until the blastocyst stage or arrest. Embryos were disaggregated and all cells were analyzed for chromosomes 13, 18, 21, X and Y by fluorescent in situ hybridization (FISH).

Main Outcome Measure(s):
Pronuclear size, in vitro embryo development and cytogenetic characteristics.

Result(s):
All the embryos were chromosomally abnormal (7.4% diploid mosaic, 16.7% haploid mosaics, 5.5% aneuploid mosaic and 70.4% chaotic mosaic), and 35.2% showed a Y chromosome. No difference in the pronuclear size was observed according to the type of abnormality. Only 7.4% of the embryos resulted in good morphology blastocysts.

Conclusion(s):
Despite of showing only one pronucleus, most of the zygotes resulted from fertilization. Embryos derived from 1PN ICSI zygotes are chromosomally abnormal. Neither the pronuclear size nor the in vitro developmental ability of these embryos can be predictive of their chromosomal constitution. According to our results, embryos that develop from 1PN ICSI zygotes should be discarded for any reproductive purpose.

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