Separate influences of birth order and gravidity/parity on the development of systemic sclerosis

OBJECTIVE

Birth order has been valuable in revealing the role of environmental influences on the risk of developing certain diseases such as allergy and atopy. In addition, pregnancy has profound effects on the immune system such as short-term effects that permit fetal survival as well as longer-term effects that could influence late-onset diseases. In order to better evaluate these influences, we studied the association of birth order and gravidity/parity as risk factors for systemic sclerosis (SSc; scleroderma).

METHODS

Data regarding SSc cases and their unaffected sibling controls were obtained from the Scleroderma Family Registry and DNA Repository. The case-sibling design was used to minimize confounding due to differences in age, race, ethnicity, or calendar time. The gravidity/parity analysis was based on sibships with at least one SSc-affected and one unaffected sister.

RESULTS

Birth order was examined in 974 sibships, comparing SSc cases (n = 987) with their unaffected siblings (n = 3,088). The risk of scleroderma increased with increasing birth order (odds ratio [OR] 1.25, 95% confidence interval [95% CI] 1.06-1.50 for birth order 2-5; OR 2.22, 95% CI 1.57-3.15 for birth order 6-9; and OR 3.53, 95% CI 1.68-7.45 for birth order 10-15). Gravidity/parity was analyzed in 168 sibships (256 unaffected sisters, 172 SSc cases). We found an association between a history of one or more pregnancies and SSc (OR 2.8).

CONCLUSION

Birth order and pregnancy were independently associated with a higher risk of developing SSc. These findings suggest that immune development in early childhood and/or pregnancy-associated events, including but not limited to microchimerism, plays a role in SSc susceptibility.

Effect of gonadotrophin releasing hormone on levels of luteinising hormone in cattle synchronised with dinoprost

Synchronisation of oestrus was achieved in a group of three cows and two heifers with dinoprost. Sixty-six hours after the second injection of dinoprost, 0.125 mg synthetic gonadotrophin releasing hormone (GnRH) was given intramuscularly. Concentrations of luteinising hormone (LH) were monitored in peripheral blood and close grouping of preovulatory LH peaks was seen around 2.5 hours after injection of GnRH.

Plasma progesterone and luteinising hormone levels in cattle after synchronisation of oestrus with dinoprost

The plasma levels of progesterone and luteinising hormone (LH) were monitored in a group of cattle after pretreatment with two injections of 25 mg dinoprost. Close groupings of preovulatory LH peaks were observed and the possible significance of this is discussed. Based on the findings of this study, supporting evidence is provided for the timing of insemination after injection of cattle which have been synchronised for oestrus with dinoprost.