A new study published in the Annals of the Rheumatic Diseases finds that compared to females born with average birth weight, those born with heavy birth weight are two times as likely to develop rheumatoid arthritis when they become adults. Rheumatoid arthritis is a condition that occurs when the immune system attacks the joints, lungs or skin and results in inflammation, pain, and loss of functioning mobility.

Researcher L A Mandl (Division of Rheumatology, Hospital for Special Surgery, Weill Cornell Medical College) and colleagues argue that these findings support the fetal origin of disease theory. That is, factors that occur during pregnancy program an individual to be more prone to certain diseases and conditions in adult life. For example, previous research has linked low birth weight to conditions such as diabetes, coronary heart disease, and high blood pressure, and high birth weight has been associated with an increased risk of breast cancer and leukemia.

These new findings on rheumatoid arthritis development come from a survey of more than 87,000 women, age 30 to 55, who took part in the US Nurses’ Health Study from 1976 and 2002. In two year intervals, the women responded to questions about their health, lifestyle, and family illness. In 1992, researchers asked them questions about birth weight.

Between 1976 and 2002, 619 women received their first diagnosis of rheumatoid arthritis. The average birth weight was between 3.2 to 3.85 kg, and women who weighed over 4.45 kg at birth were found to be twice as likely to develop the autoimmune disease known as rheumatoid arthritis. These findings held after the researchers statistically controlled for factors that may influence birth weight such as socioeconomic status, parental smoking, maternal diabetes, age at first period, use of oral contraceptives or hormone replacement therapy, breastfeeding and weight.

Though the authors do not have a clear biological explanation for their results, they do note that abnormal hormone regulation – a process thought to affect a baby while in the womb – is prevalent in adults with rheumatoid arthritis.

The authors conclude that: “The biology underlying this association is speculative, and the relative importance of fetal nutrition versus genotype is unknown. However, if fetal nutrition has an impact on future risk of RA [rheumatoid arthritis], this could be a potentially modifiable risk factor. Further study of our observation that high birth weight is associated with an increased risk of RA could provide insight into the pathogenesis of RA. These data also provide further evidence for the importance of fetal environment as a crucible for future adult diseases.”

Is birthweight associated with risk of rheumatoid arthritis? Data from a large cohort study
L A Mandl, K H Costenbader, J F Simard, E W Karlson
Annals of the Rheumatic Diseases (2008).
doi 10.1136/ard.2007.080937]
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Written by: Peter M Crosta