New York (PTI): Heavy birthweight female babies are twice as likely to develop rheumatoid arthritis, a painful joint condition, later in life than their average birthweight peers, according to a new study.

Researchers have based their findings on over 87,000 women taking part in the US Nurses' Health Study between 1976 and 2002. All the participants were aged between 30 and 55 at the start of the study in 1976.

Every two years, the women were quizzed about their health, lifestyle, and family illness. And in 1992, they were asked to provide information on their birthweight.

During the study period, 619 women were diagnosed with rheumatoid arthritis for the first time -- those who weighed more than 4.54 kg at birth were twice as likely to develop the autoimmune disease as those who weighed between the average of 3.2 to 3.85 kg at birth.

The results held true after taking into consideration factors likely to influence the baby's birthweight like age at first period, socioeconomic status, parental smoking, maternal diabetes, use of oral contraceptives or HRT, and weight.

According to the researchers, there is no obvious biological explanation for the findings. "But adults with rheumatoid arthritis have abnormal hormone regulation, and it is thought that this process may be triggered while in the (mother's) womb."

Although completely speculative, the researchers have suggested that if the risk of rheumatoid arthritis can be lessened during pregnancy, altering the mother's diet could open up an exciting avenue for prevention.

The study has been published in the latest edition of the 'Annals of Rheumatic Diseases' journal.