Size at Birth and Cardiovascular Responses to Psychological Stressors: Evidence for Prenatal Programming in Women

Background: Epidemiological studies have repeatedly shown inverse associations between size at birth and blood pressure in later life. There is some evidence to suggest that exaggerated blood pressure responses to psychological stressors are a forerunner of sustained hypertension.

Objective: To determine whether individuals who were smaller at birth have greater blood pressure and heart rate responses to psychological stressors.

Design: Prospective cohort study.

Methods: A total of 104 men and 79 women (mean age 26.3 years) were recruited from the Adelaide Family Heart Study cohort. Blood pressure was monitored continuously throughout the study using a Portapres and participants undertook a series of three stress tests: Stroop, mirror drawing and public speech. The stress response was defined as the increment from baseline to the mean blood pressure during the three tasks.

Results: In women, a 1 kg increase in birthweight was associated with an 8.7 mmHg (95% confidence interval: 3.6-13.8, P = 0.001) reduction in the systolic and a 4.1 mmHg (1.6-6.6, P = 0.002) reduction in the diastolic response to stress. The heart rate response to stress was also inversely related to birthweight. These results remained significant after correction for gestational age and other potential confounding factors. Similar results were found for birth length and head circumference. There were no such relationships in men.

Conclusions: This study provides the first human evidence that cardiovascular responses to psychological stressors may be programmed antenatally and suggests a potential mechanism linking reduced fetal growth with raised blood pressure and cardiovascular disease in later life.