(HealthDay News) – For women, higher offspring number and higher parity are associated with a reduced risk of first clinical demyelinating event (FCD).

To investigate the association between pregnancy, offspring number, and FCD risk, Anne Louise Ponsonby, PhD, of the Murdoch Childrens Research Institute in Melbourne, Australia, and colleagues studied 282 cases (aged 18–59 years) with a first clinical diagnosis of central nervous system (CNS) demyelination and 542 age-, gender-, and study region-matched controls without a CNS demyelination diagnosis.

The researchers found that, for women, but not men, a higher number of offspring was associated with FCD risk (P = 0.001 and 0.71, respectively). Higher parity among women correlated with a significantly reduced risk of FCD (adjusted odds ratio [OR], 0.51 per birth). The effect size was similar for classic first demyelinating events (adjusted OR, 0.47). Among parous women only, the apparent beneficial effect of higher parity was evident. For cases with low, but not high (four or more), offspring number, there was a clear female excess. The association between higher parity and reduced FCD risk among women was not modified by factors such as human leukocyte antigen DR15 genotype.

“Temporal changes toward an older maternal age of parturition and reduced offspring number may partly underlie the increasing female excess among multiple sclerosis cases over time,” the authors write.

Two authors disclosed financial ties to Bayer Schering Pharma. One of the authors hold patents pertaining to the study.

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