March 11, 2002

NEW YORK (Reuters Health)--Stress experienced by a mother during pregnancy appears to influence how her baby's brain and nervous system will react to stressful events, researchers report. They believe this conditioning may increase a child's vulnerability to various physical and mental illnesses in later life.

"Factors related to medical, endocrine and psychosocial stress during human pregnancy may negatively impact fetal brain development and function," report Dr. Pathik Wadhwa and colleagues from the University of Kentucky in Lexington. Their findings were presented at the 20th annual Scientific Sessions of the Society of Behavioral Medicine held in San Diego, California, earlier this month.

Previous research has suggested that highly stressed mothers-to-be have a higher risk of delivering premature and underweight infants, compared with less-anxious mothers.

In their study of 156 mother-fetus pairs, the investigators sought to determine the relationship between an expectant mother's psychological state and her fetus' response to stressful stimuli.

To do so, they monitored fetal heart rate while disturbing the fetus with a vibroacoustic stimulator (a small vibrating device), placed upon the mother's abdomen. These devices are commonly used by obstetricians to awaken a sleeping fetus.

The authors report that "the magnitude and duration of the fetal heart rate changes in response to (the device) was greater in women with ... high levels of stress hormones ... high levels of psychological stress, and low levels of social support" compared with women with less stress.

Over time, fetuses appeared to become "habituated" to occasional vibroacoustic stimulation so that their stress responses, as indicated by increased heart rate, subsided with each new stimulation. However, the research team reports that this learning process was "delayed" in fetuses carried by highly stressed women - in other words, their stress responses remained on 'alert' mode despite repeated stimulation.

Wadhwa and colleagues believe these findings support the theory that maternal stress hormones influence fetal brain development. They believe that these early neurological changes could also increase a child's lifelong vulnerability to "a host of (stress-related) chronic mental and physical degenerative conditions," including heart disease and its attendant risk of heart attack and stroke.

Stress early in pregnancy may increase risk of birth defects
December 15, 1999

NEW YORK (Reuters Health) -- Stressful events around the time of conception and during the first trimester of pregnancy may increase the risk of birth defects (or congenital abnormalities), according to results of a study.

Drs. Suzan L. Carmichael and Gary M. Shaw, from the March of Dimes/California Birth Defects Monitoring Program in Emeryville, analyzed the relationship between stressful events in a woman's life from 1 month before conception to 3 months into pregnancy, and the risk of the fetus having birth defects.

The researchers interviewed over 2,000 mothers by telephone, including 207 who had children with cardiovascular abnormalities, 265 who had children with skull or spinal cord defects, 662 who had children with cleft lip and/or palate, 165 who had children born with limb defects, and 734 mothers of children who did not have birth defects.

In the interviews, which took place about 3-1/2 years after the pregnancy, the mothers were asked if any of three events had taken place around the time of conception or during the first trimester: someone "very close" dying; the mother or someone close to her getting separated or divorced; or the mother or someone close to her losing a job. The women were also asked about a variety of health-related behaviors.

The research team found that mothers who reported one or more stressful life events were slightly more likely to have babies with birth defects. The chances of having a baby with cardiovascular defects was 1.4 times higher; the chances of having a baby with skull or spinal problems, 1.5 times greater; of having a baby with cleft lip and/or palate, about 1.4 times greater; and of having a baby with a limb anomaly, 1.3 times greater.

For all four types of abnormality, the relationship between stress and risk of defects was significantly less in obese women. The authors suggest that the "stress system" may be less active in obese women, thus protecting the fetus from harm.

On the other hand, the relationship between stress and risk of defects was significantly greater in women with lower levels of education. The authors suggest that education level may reflect socioeconomic status, pointing out "the chronic stressors, behaviors, and conditions that often go along with lower socioeconomic status... may increase the impact of stressful life events on fetal development."

Writing in the January issue of Epidemiology, Carmichael and Shaw listed several ways that stress might affect a developing fetus, for example, changing levels of body chemicals such as catecholamines and corticosteroids that would affect the fetal environment, or causing the mother to engage in "harmful coping behaviors" such as smoking, drinking, or poor nutrition.

The authors also note that "recall bias" could explain their findings: women who had babies with defects might tend to remember stressful events around the time of conception more frequently than mothers of babies without problems. They explain that their study does not allow them to rule out this problem, so more research is needed.