All other things being equal, parents scored 4.5 points lower than non-parents in systolic blood pressure (the top number) and 3 points lower than non-parents in diastolic blood pressure. Holt-Lunstad says the size of the difference is statistically significant, but she warns against hastily making major life changes based on this finding alone.

from Brigham Young University. “Raising Kids May Lower Blood Pressure.” Science Daily 14 January 2010.

The effect is even larger for mothers than fathers, but the research only covered people with children living with them.  I suspect that we’re not likely to make any more major life changes at this stage, like persuading the children to move back home or adopting more.