A new study has suggested that stress hormone levels prior to pregnancy could affect a woman's risk of delivering a low birth weight baby. Generally, when you wake up in the morning, levels of the stress hormone cortisol are high and they go down as the day passes. However, the study authors said that some people have a low cortisol level when they get up in the morning, and a below normal decline during the day.

The researchers said that it could be linked to chronic stress and trauma history. The abnormal pattern has also been associated with the progression of many diseases, like cancer and hardening of the arteries. It could also predict the weight of unborn baby.

In a news release, study author Christine Guardino, a postdoctoral scholar in psychology at the University of California, Los Angeles, said that they have discovered that the same cortisol pattern that was associated with chronic stress is also linked to the delivery of an underweight baby.

During the study, she along with her colleagues analyzed 142 expected women in different areas, including Baltimore, Lake County, Ill., eastern North Carolina, Los Angeles and Washington, D.C.

To know the stress levels of the women, the researchers studied different factors such as blood pressure, body mass index, cortisol levels in their saliva among many others.

Published online recently in the journal Health Psychology, the study suggested that the cortisol patterns of a mother prior to pregnancy affect the birth weight of the baby.

In the United States, over 300,000 babies with a low birth-weight take birth every year. At the time of birth, they weigh below five-and-a-half pounds. Such infants face high risk of health issues and are even prone to death.