Even before a woman becomes pregnant her stress physiology may predict a lower-birth-weight of the baby -- less than 2.5 kg said a new study. The findings revealed that the mother's stress physiology before she even conceives is also important. It suggests that a woman's health and life circumstances before her pregnancy especially chronic stress matter greatly. We found that the same cortisol pattern that has been linked with chronic stress is associated with delivering a baby that weighs less at birth said lead author Christine Guardino from the University of California in the US. Researchers claim this study first