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Chromosome anomalies in early human embryos
R R Angell1, S G Hillier, J D West
1Department of Obstetrics and Gynaecology, University of Edinburgh, U.K.
Journal of Reproduction and Fertility. Supplement
|January 1, 1988
Summary
Human embryos fertilized in vitro show high rates of chromosomal abnormalities, with 23% of preimplantation embryos and 30% overall exhibiting errors like aneuploidy and triploidy.
Area of Science:
- Reproductive biology
- Human genetics
- Embryology
Background:
- Chromosomal abnormalities are a significant cause of pregnancy loss and developmental issues.
- In vitro fertilization (IVF) procedures may influence early embryonic development and chromosome segregation.
Purpose of the Study:
- To investigate the frequency and types of chromosomal abnormalities in human preimplantation embryos resulting from in vitro fertilization.
- To compare the incidence of chromosomal errors in IVF embryos with those observed in clinically recognized pregnancies.
Main Methods:
- Karyotyping of human preimplantation embryos obtained from an unselected group undergoing in vitro fertilization.
- Analysis of oocytes with three pronuclei (tripronucleate oocytes) as a separate group.
Main Results:
- Seven out of 30 (23%) studied preimplantation embryos exhibited chromosomal abnormalities, primarily aneuploidy (trisomy and monosomy).
- One oocyte presented a structural chromosomal abnormality.
- Nine percent of oocytes were tripronucleate, a rate higher than in clinically recognized pregnancies, suggesting superovulation effects.
- When including tripronucleate embryos, 10 out of 33 (30%) embryos were considered abnormal.
Conclusions:
- A significant proportion of human preimplantation embryos from IVF display chromosomal abnormalities, with frequencies comparable to clinically recognized pregnancies when accounting for factors like maternal age and monosomy lethality.
- The higher rate of tripronucleate oocytes in IVF may be linked to superovulation protocols.
- The origins of these chromosomal errors remain multifactorial, potentially involving gamete quality or environmental influences during fertilization.