After finding the genes for this and that, researchers are now starting to find the genes responsible for triggering birth itself.

Does this mean that without these genes, we would not be born? Not quite. Instead, birth-triggering genes represent the first crucial step in the delivery process. A first step during which these genes send a signal to the body, saying, in effect, "get ready, it's time!"

A number of scientists have been looking for such signals for years in the hope of better understanding what triggers premature births. In theory, if we can identify people who have defective birth-triggering genes, we can predict the probability of a premature delivery and, at the same time, prevent it.

But if one is to believe the articles published about a recent discovery, this next step is a big one. "The process of delivery is complex," explains Radek Bukowski of the University of Texas, lead researcher of the team whose research appeared in the journal Public Library of Science .

To identify which genes activate during labour, Bukowski's team measured levels of RNA in tissues collected from the cervix and different parts of the uterus in women who gave birth naturally and in others who underwent cesarean sections. At least 500 genes showed changes in activity, and of these, 14 groups of genes were common to the upper part of the uterus and 14 others were common to the lower part, including genes associated with muscle contraction.

Muscle contraction is obviously the key because when the upper portion of the uterus contracts, the lower portion relaxes, opening a passage for the baby. Do the 14 groups of "upper" genes work together to first trigger the process of muscle contraction, which in turn triggers the opening of the cervix? But if so, what tells them it's time to start labour?