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Impaired Stress Hormone before Pregnancy Predicts Lower-birthweight Babies

  Impaired Stress Hormone before Pregnancy Predicts Lower-birthweight Babies

Illustration: Maja Moden

Before women even become pregnant, their biological profile may predict a lower-birthweight baby, a UCLA-led research team found. The study analyzed 142 women who were participating in a larger study that was conducted by the Community Child Health Network (CCHN), which looked at how chronic stress affects new parents and their babies. The subjects were chosen for the UCLA-led research because they provided daily saliva samples, and they became pregnant again during the CCHN study. The research, which found the women were more likely to give birth to lower-weight babies, is the first evidence that maternal cortisol patterns before conception influence the weight of the baby.

“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,” says Christine Guardino, PhD, a UCLA postdoctoral scholar in psychology.

More than 300,000 babies in the U.S. are born each year with low birth weight, meaning they weigh under 2,500 grams, or less than about five-and-a-half pounds. They have an above-average risk for infant mortality, developmental problems and health abnormalities throughout their lives, including cardiovascular and metabolic disorders.

The UCLA-led research looked at families in five different regions — Los Angeles, California; Washington, D.C.; Baltimore, Maryland; Lake County, Illinois; and eastern North Carolina — beginning a month after the birth of a child and again when the child was 6, 12 and 18 months. Previous studies have shown the importance of stress hormones during pregnancy for fetal growth and development, but the new study provides the first evidence that the mother’s stress physiology before she even conceives also is important.

Chris Dunkel Schetter, PhD, professor of psychology, said women planning a pregnancy should take into account the possible effects of stress and begin planning for a healthy first pregnancy well in advance.

The study evaluated mothers who are African-American, Latino or Hispanic and white non-Hispanic. A majority of them have household incomes near or below the federal poverty level, which in 2013 was $23,550 for a family of four. The mothers were affected by stress triggered by numerous sources, ranging from finances, family relationships and neighborhood issues to major life events such as the death of a family member, interpersonal violence and racism.

The researchers gauged the subjects’ stress levels based on measurements of their blood pressure, body mass index, the level of cortisol in their saliva and other factors, which collectively offer insight into how the body’s systems age in response to stress. The researchers also interviewed mothers and fathers in their homes. Drs. Guardino and Dunkel Schetter and others are conducting follow up research on some of the children, now between 3 and 5 years old, from the original study.

“Diurnal Salivary Cortisol Patterns Prior to Pregnancy Predict Infant Birth Weight,” Health Psychology, February 4, 2016


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