Maternal age effect on early human embryonic development and blastocyst formation

Area of Science:

• Reproductive biology
• Human embryology
• In vitro fertilization

Background:

• Female fertility naturally declines with age.
• This decline may be due to uterine or oocyte quality.
• This study investigates the impact of aging oocytes on embryo development.

Purpose of the Study:

• To examine the hypothesis that aging oocytes contribute to age-related fertility decline.
• To assess embryo development to the blastocyst stage in relation to patient age.
• To evaluate blastocyst formation and expansion rates based on oocyte age.

Main Methods:

• In vitro fertilization (IVF) and embryo coculture.
• Assessment of blastocyst formation rate ([blastocysts/embryos on day 2]*100).
• Evaluation of blastocyst expansion rate ([expanded blastocysts/blastocysts]*100) relative to patient age.

Main Results:

• Oocyte yield decreased with age, but cleavage rates remained stable.
• Preimplantation embryo development to blastocysts declined in women over 30, with increased morula stage arrest.
• Blastocyst expansion rate showed a negative linear relationship with patient age.
• The proportion of patients achieving at least one expanded blastocyst significantly decreased with age (82% <30 years vs. 36% >=40 years).
• A high delivery rate (25.8%) was observed in patients over 40 after blastocyst-stage embryo transfer.

Conclusions:

• Increasing patient age leads to a decline in human embryo quality originating from aging oocytes.
• Potential causes include chromosomal abnormalities, oocyte-derived factors, and altered genomic activation timing.
• Embryo quality and developmental potential are significantly impacted by oocyte aging.