Blastocyst Success Rates by Age: A Breakdown

In Vitro Fertilization (IVF) often involves the transfer of a blastocyst, an embryo that has developed for several days after fertilization. The likelihood of this procedure resulting in a successful pregnancy is closely linked to many factors, with maternal age being one of the most prominent.

Understanding Blastocysts in IVF

A blastocyst is an embryo that has developed for five to seven days after fertilization, featuring two distinct cell types: the inner cell mass (ICM), which develops into the fetus, and the trophectoderm, which forms the placenta. Culturing embryos to this advanced stage is a common practice because it allows embryologists to better identify which embryos have the highest potential for implantation.

Transferring a blastocyst is associated with a higher implantation rate per transfer than a less-developed embryo. The quality of a blastocyst is visually assessed in the laboratory using a grading system that considers its expansion, the inner cell mass, and the trophectoderm. Success is measured by implantation, a clinical pregnancy confirmed by ultrasound, and ultimately, a live birth.

How Maternal Age Impacts Blastocyst Quality

Maternal age influences fertility because the quality of a woman’s eggs, or oocytes, declines over time. This natural process leads to an increased likelihood of chromosomal errors within the eggs.

This decline in egg quality directly affects the resulting blastocysts, leading to a higher rate of aneuploidy—a condition where an embryo has an incorrect number of chromosomes. Aneuploid blastocysts are a primary cause of implantation failure and early pregnancy loss. The rate of aneuploidy in blastocysts rises from around 30% in women under 35 to over 90% in women in their mid-40s.

Older women also produce fewer eggs during an IVF cycle. This smaller number of eggs provides fewer opportunities to create embryos, which means fewer may develop into blastocysts.

Blastocyst Live Birth Success Rates by Age Group

The probability of a live birth following a blastocyst transfer decreases as maternal age increases, reflecting the changes in egg quality. These figures are population averages, as individual outcomes can be influenced by personal health factors.

For women under 35, the chances of a live birth per transfer are highest, with rates as high as 64%. For those aged 35 to 37, the rate is around 61%, while the 38 to 40 age bracket sees a drop to approximately 45%.

The decline becomes more pronounced for women in their early 40s. The live birth rate for ages 41 to 42 may fall to around 32%. Beyond age 42, chances decrease significantly to 20% or lower, with some statistics placing the rate as low as 5% for women aged 43 to 44.

The Role of Preimplantation Genetic Testing (PGT-A)

Preimplantation Genetic Testing for Aneuploidy (PGT-A) is a technology that screens for chromosomal abnormalities. It involves taking a small biopsy from the trophectoderm of a blastocyst to identify euploid, or chromosomally normal, embryos for transfer. By selecting a euploid embryo, PGT-A can increase the likelihood of a successful pregnancy per transfer and may reduce the rate of miscarriage.

This testing is particularly relevant for women of advanced maternal age, as it helps avoid transferring an embryo with no potential to result in a healthy baby. PGT-A is a selection tool, not a method for correcting embryos. In some cases, testing may reveal that none of the available blastocysts are euploid.

While PGT-A is highly accurate, limitations such as mosaicism—where an embryo has both normal and abnormal cells—can complicate interpretation.

Navigating Options with Advanced Maternal Age

For individuals of advanced maternal age pursuing IVF, open discussions with fertility specialists are important. These conversations help establish realistic expectations based on individual circumstances and diagnostic testing.

For those facing low probabilities of success with their own eggs, using donor eggs is an effective alternative. Success rates are then determined by the age of the egg donor, not the recipient. Since donors are young and screened for health, the resulting blastocysts have a much lower rate of aneuploidy.

Live birth rates per transfer with donor eggs can be 50% or higher, regardless of the recipient’s age. This option offers a successful path to parenthood by bypassing the biological hurdle of diminished egg quality.