To what extent the conditions we encounter before birth influence our individual characteristics? It‘s the question at the center of fetal origins, a relatively new field of research that measures how the effects of influences outside the womb during pregnancy can shape the physical, mental and even emotional well-being of the developing baby for the rest of its life.

Science writer Annie Murphy Paul calls it a gray zone between nature and nurture in her book Origins, a history and study of this emerging field structured around a personal narrative -- Paul was pregnant with her second child at the time. What she finds suggests a far more dynamic nature between mother and fetus than typically acknowledged, and opens up the possibility that the time before birth is as crucial to human development as early childhood.

Read Annie Murphy Paul's essay on CNN.com>>