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C. Identifying a Crucial Molecular Step in Pregnancy

Narrator: This is Science Today. Researchers have identified the first molecular step that allows a week-old human embryo to attach to the uterine wall. Dr. Susan Fisher of the University of California, San Francisco led the study and says this early stage of human implantation depends upon a molecular adhesion process in which the release of sticky substances stops the rolling embryo and causes it to attach to the uterus.

Fisher:This is the first report of what may be the first step in implantation. It's long been known that there's a very transient step in adhesion called apposition, where the embryo is very loosely associated with the uterine wall. It was unknown what the basis for that loose association was. And we're proposing that it is this rolling adhesion mechanism.

Narrator: Understanding this mechanism may someday provide a new tool to diagnose and treat infertility and miscarriage. For Science Today, I'm Larissa Branin.