There's some good news for all you pregnant mamas older than 40: Abnormalities detected in early embryos are not a sure sign a baby will be born with a birth defect.
Along with her colleagues, she studied mouse embryos with a 50-50 mix of normal and abnormal cells. What they found was that up to half of abnormal cells discovered in early stages of pregnancy can be eliminated and replaced by healthy cells.
"The embryo has an amazing ability to correct itself," Zernicka-Goetz said. "We found that even when half of the cells in the early-stage embryo are abnormal, the embryo can fully repair itself. If this is the case in humans too, it will mean that even when early indications suggest a child might have a birth defect...this isn't necessarily the case."
These findings will definitely raise questions about the ethics of terminating an embryo after discovering abnormal cells, especially because many expectant mamas are forced to make difficult choices based on test results they don't really understand. "What does it mean if a quarter of the cells from the placenta carry a genetic abnormality?" asked Zernicka-Goetz. "How likely is it that the child will have cells with this abnormality, too? Given that the average age at which women have their children is rising, this is a question that will become increasingly important."
Still, Zernicka-Goetz—who gave birth at 44—says older moms whose embryos are at greatest risk of developing genetic abnormalities, and who are generally offered tests to predict ther likelihood, should be "reassured" by these findings. She and her team will now try to determine the exact proportion of healthy cells needed to completely repair an embryo.
"I am one of the growing number of women having children over the age of 40," she said. "I know how lucky I was and how happy I felt when Simon was born healthy. It was a traumatic experience but it led me to do something positive about it."