Increased blood pressure in neonates and infants whose mothers smoked during pregnancy

To determine whether maternal smoking during pregnancy is associated with increased blood pressure (BP) in neonates.

We measured BP in the following groups: (1) 73 neonates of mothers who smoked during pregnancy, (2) 43 neonates of mothers who quit smoking early during pregnancy, (3) 83 neonates of passive smoking mothers, and (4) 170 neonates of nonsmoking parents. Three BP measurements were made at 1, 24, 48, and 72 hours of life. Some of the neonates were followed for 2 years.

We observed a significant positive correlation between the number of cigarettes smoked by the mothers during pregnancy and the BP of the neonates. From the first to the seventy-second hour of life the BP in the infants of the mothers who smoked 15 or more cigarettes per day was significantly higher than in the infants of the nonsmoking mothers, whereas the increase in BP was intermediate when the mothers smoked 7 to 15 cigarettes per day. The BP was similar to that of the control subjects when the mothers smoked 3 to 5 cigarettes per day, were passive smokers, or quit smoking during pregnancy. On reexamination between 4 and 9 months and at 12 months, in infants of mothers who smoked 15 or more cigarettes per day both the systolic and the diastolic BP were significantly higher than in the control subjects; at 12 months 5 of the infants of mothers who smoked cigarettes had BP greater than the 95th percentile for age and gender. At 24 months of life there was no significant difference in systolic or diastolic BP between infants of smoking and nonsmoking mothers.

Neonates and infants of mothers who smoked during pregnancy have an elevation of BP that is related to the number of cigarettes smoked per day. Smoking 15 or more cigarettes per day may cause BP elevation in infancy, but the BP returns to normal during the second year of life.