Birth Order and Health
Researchers do not just study intelligence and personality when looking at birth order. They have become involved in many other areas, including health risks. One is the chance of a child having Type 1 diabetes as a consequence of his or her position in the family. A study done in Norway followed 1.4 million children between 1974 and 1998. Some of the study's findings apparently indicate a correlation between birth order and the onset of Type 1 diabetes and the ages of the parents. While there was no association between maternal age when the first baby was born, the study showed a tendency toward diabetes among second- or later-born children for each five-year increase in maternal age. In fact, 43.2 percent of all fourth-born children studied suffered an onset of Type 1 diabetes. The father's age, however, was not a factor in any of the families.
When a woman has babies after age 30, she is more likely to have a child or children with lower birth weight, as well as complications during pregnancy. The study offers that these, and other factors contribute to later-born children developing Type 1 diabetes. So, it is not so much the birth order as it is the age of the mother - the later the birth of the second or later child, the greater the overall health risks to that child.
Yet another factor presenting a higher risk of diabetes in later-born children is also age-associated. When a woman begins having babies at a later age, she usually gives birth in less-frequent intervals than women who started having children at a younger age. Women who become pregnant later have more stillbirths and pregnancy complications than do younger women. Further, there is an environmental factor: Women over age 30 have been exposed more frequently to infections and environmental toxins, thus changing somewhat their immune system's ability to respond fully effectively to infections and external effects. The researchers say this is a serious concern, particularly for second, third, and fourth-born children.