Well, the eldest of the brood has a new reason to believe he or she got the shaft. That’s because being the oldest (or only) child may increase the risk of developing diabetes or high blood pressure, according to new research in the Journal of Clinical Endocrinology and Metabolism.

The study, conducted at Auckland’s Liggins Institute in New Zealand, found that the first-born has more trouble absorbing sugars into the body and that they have higher daytime blood pressures than children who have older siblings. Indeed, researchers documented a 21 percent drop in insulin sensitivity among first-born children.

“Birth order alone is not a predictor of metabolic or cardiovascular disease, but being the first-born child in a family can contribute to a person’s overall risk,” said researcher Wayne Cutfield, in a statement.

In the study, when researchers monitored 85 healthy children (ages four to 11) and measured fasting lipid and hormonal profiles, as well as height, weight and body composition, they found that the 32 first-born participants had a 21 percent reduction in insulin sensitivity and a 4 mmHg increase in blood pressure compared to those who were not the first-born in their families.

Such differences, posit the researchers, may be the result of physical changes in the mother’s uterus during her first pregnancy, and an increase in nutrient flow that may occur with subsequent pregnancies.

The metabolic differences in younger siblings might be caused by physical changes in the mother’s uterus during her first pregnancy. As a result of the changes, nutrient flow to the fetus tends to increase during subsequent pregnancies.

More research is needed to discover whether and how this data would translate in adult cases of hypertension and/or diabetes.

Does this finding surprise You?