In a follow-up study done by the Karolinska Institute in Stockholm, Sweden, researchers found that blood pressure (BP) readings were higher in young men who were born prematurely. A previous study had shown that low birth weight in males was connected to higher adult BP, but, as Stefan Johansson, MD, of the Institute noted, "we found that preterm birth provides a higher risk than just being small at [birth]."
The findings, which were published in a report in Circulation: Journal of the American Heart Association, came from a study of 329,495 Swedish men born between 1973 and 1981 who had BP measurements recorded at age 20. Full-term, moderately preterm, very preterm, and extremely preterm births were defined as births which took place at 37 to 41 weeks gestation, 33 to 36 weeks, 29 to 32 weeks, and 24 to 28 weeks, respectively.
The risk of high systolic BP increased steadily from 25% for moderately preterm to 93% for extremely preterm, compared with full-term births. Being small for the length of pregnancy was only a risk factor for high BP among men born at >33 weeks.
The reasons for the link between gestational age and BP are not clear but "could involve structural changes in the vascular tree," Dr. Johansson said. Hormone alterations could also be a factor.