New research may potentially improve the chances of success for some women and couples looking to get pregnant through in vitro fertilization.
IVF has been around for nearly four decades, but the procedure still has a relatively low success rate due, in large part, to genetic and chromosomal mutations in embryos that can be difficult to detect. While various methods have been developed to identify such mutations for selecting those with the highest chances of resulting in a successful pregnancy, their accuracy remains challenging.
In a study published Monday in the Proceedings of the National Academy of Sciences, researchers from the United States and China describe a method that they said for the first time combines the latest in gene sequencing technologies with other genomic-based strategies to identify those mutations, leading to better detection and allowing for the improved selection of human embryos for IVF.
Two healthy babies were born after the method was used to select embryos.
Dr. Jason Franasiak, an infertility specialist at the Rutgers Robert Wood Johnson Medical School, described the technique as a “safe, accurate, and cost-efficient means for performing comprehensive chromosome screening, and single-gene defect diagnosis.” Franasiak was not involved in the study.
One reason for the relatively low IVF success rate — from as high as about 40 percent for women under the age of 35 to as low as about 12 percent for women over the age of 40 — is what is known as a chromosomal aneuploidy, when a cell does not have the normal count of 46 chromosomes. Another factor are alterations in a single gene, or when a gene is missing.
Separate genetic technologies can detect aneuploidies or single-point mutations, but they had not been able to detect both abnormalities at the same time. The new method — dubbed MARSALA, short for mutated allele revealed by sequencing with aneuploidy and linkage analyses — combines both into one simple approach.
The researchers tested MARSALA on two couples undergoing IVF. Both cases involved parents in their early 30s — one in which the father harbored a genetic mutation that caused multiple bony spurs and lumps to grow in his body; another in which the mother carried a recessive mutation on one of her X chromosomes that she had already passed on to one son, who now suffers from hair, sweat, and skin abnormalities. By using MARSALA, the researchers selected mutation-free embryos for the two couples, each resulting in the birth of a healthy girl free of the parents’ genetic problems.
The scientists noted that the method is limited to parents who already have known genetic disorders, and cannot be used for the general population. But in those cases, they write, “MARSALA has improved the precision” of diagnostic and screening techniques for IVF embryos.
Not all reproductive medicine doctors agree. Dr. Michael Alper, medical director of Boston IVF, said MARSALA could have a place in the clinic for some couples. But Dr. Francesco Fiorentino, president and CEO of Genoma Molecular Genetics Laboratory in Rome, said the method mostly serves to “simplify the laboratory workflow” without offering much improvement at the patient level.
Fiorentino noted that MARSALA still can’t pick up on a phenomenon called mosaicism, in which a person’s cells have a different genetic makeup — a common problem in IVF-derived embryos. This, he said, undermines “the reliability of the results.”