Genetics, Mosaic Embryos, and Your Fertility with guest Meaghan Doyle

Mosaic embryos—those with a mix of normal and abnormal cells—are far more viable than commonly believed, and dismissing them based on outdated assumptions could mean losing the chance at a healthy baby. Genetic counselor Meaghan Doyle debunks the myth that high-level mosaicism automatically means failure, revealing that segmental mosaics (where only a portion of a chromosome is affected) actually have the highest success rates in IVF. The key insight? Embryos can self-correct: abnormal cells die off early, and healthy ones repopulate the embryo, leading to normal development. This biological repair process is why amniocentesis—testing fetal cells directly, not placental DNA—is the gold standard for confirming a healthy pregnancy after a mosaic transfer. Doyle emphasizes that mosaicism isn’t tied to maternal age, challenging the idea that older patients face double the risk of chromosomal issues. She urges patients to advocate for labs that report mosaicism and to demand full transparency in fertility care, arguing that informed consent—not default decisions by clinics—should guide treatment. The episode dismantles long-standing fears around genetic testing in fertility, showing that pre-implantation genetic testing for aneuploidy (PGT-A) isn’t just for older patients or those with recurrent loss. It’s a tool for everyone, especially when paired with genetic counseling.