Effects of alcohol and smoking during pregnancy on infant autonomic control

Abstract

Prenatal exposure to smoking and alcohol increases the risk for Sudden Infant Death Syndrome (SIDS). Physiological changes associated with these exposures are not well studied. Full-term infants were tested within the first 3 days of life. We hypothesized that maternal alcohol consumption and/or smoking during pregnancy would alter autonomic nervous system function. Newborns whose mothers smoked during pregnancy had lower beat-to-beat heart rate variability in quiet sleep. Infants whose mothers consumed alcohol had lower global heart rate variability, but only in active sleep. Unexposed infants demonstrated increases in heart rate with head-up tilt and decreases in heart rate with head-down tilt, but smoking and alcohol-exposed infants showed no significant responses. These results indicate that autonomic function is altered by prenatal exposure to alcohol and smoking. Such markers may provide early identification of infants at greatest risk for SIDS.

FIGURE 1

This figure shows changes in heart rate (mean ± E) from the 30 s baseline period just before tilting to the average of the two 30 s blocks in the tilted position. These infants completed at least one head-up and one head-down tilt. The four groups were infants whose mothers denied smoking and consumption of alcohol at any time during pregnancy (S−/A−, n = 49), acknowledged smoking but denied consumption of alcohol during pregnancy (S+/A−, n = 24), denied smoking but acknowledged consumption of alcohol during pregnancy (S−/A+, n = 17), or acknowledged both smoking and alcohol consumption during pregnancy (S+/A+, n = 32). ** indicates the changes were significant at the .01 level.

FIGURE 2

This figure shows changes in breathing rate (mean ± SE) from the 30 s baseline period just before tilting to the average of the two 30 s blocks in the tilted position. These infants completed at least one head-up and one head-down tilt. The four groups were infants whose mothers denied smoking and consumption of alcohol at any time during pregnancy (S−/A−, n = 57), acknowledged smoking but denied consumption of alcohol during pregnancy (S+/A−, n = 28), denied smoking but acknowledged consumption of alcohol during pregnancy (S−/A+, n = 17), or acknowledged both smoking and alcohol consumption during pregnancy (S+/A+, n = 35). * and *** indicate the changes were significant at the .05 and .001 levels, respectively.

FIGURE 3

This figure shows changes in heart rate (mean ± SE) from the 30 s baseline period just before tilting to the average of the two 30 s blocks in the head-up tilted position. Based on the Substance Abuse Questionnaires, three groups were formed: infants whose mothers denied any consumption of alcohol during pregnancy (None, n = 74), Moderate exposure (greater than 0 but less than 4 drinks/month during pregnancy, n = 11), or High exposure (4 or more drinks/month during pregnancy, n = 14).