Birth order may raise the risk of first-born children developing diabetes or high blood pressure, a study has claimed.

It found that first-born children have greater difficulty absorbing sugars into the body and have higher daytime blood pressure than children who have older siblings.

The study conducted at the University of Auckland's Liggins Institute in New Zealand, measured fasting lipid and hormonal profiles, height, weight and body composition in 85 healthy kids between the ages of 4 and 11.
The 32 first-born children, who participated in the study had a 21 percent reduction in insulin sensitivity and a 4 mmHg increase in blood pressure.

The study found that the oldest and only children tended to be taller and slimmer than their later-born counterparts, even after the height and body mass index of their parents was taken into account.

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

For this study, researchers focused on kids as puberty and adult lifestyle could affect insulin sensitivity.

The study will be published in The Endocrine Society's Journal of Clinical Endocrinology and Metabolism (JCEM).