Ked if they have ever been diagnosed with the disease; of those 313 remained in the final analysis dataset, and only 73 of the 313 also had a diagnosis of RA from the Danish National Hospital discharge Registry. We do not know if the selfreported data on RA diagnosis are reliable, and whether the 240 women who did not have a recorded diagnosis in the registry were mild cases who did not get hospitalized. Including these 240 women in the analyses did not change the results (data not shown). Further, when we examined the subset of 160 women who did not have RA at conception but subsequently developed the disease, we did not find prolonged TTP to be a strong marker of future onset of RA. All of these women had a recorded diagnosis of RA between 1999 and 2008, when out-patient records were being included in the registry and thus we assumed that these correctly represented the dates of diagnosis as being after conception. The results, however,Arthritis Rheum. Author manuscript; available in PMC 2012 June 1.Jawaheer et al.Pagedid not agree with previous reports of reduced fecundity prior to onset of RA (2,3), but differences in methods as well as sources of data make the studies difficult to compare.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptThe identification of RA cases in our cohort through linkage with the Hospital Discharge Registry is likely to have introduced over-sampling of more severe cases of RA, although we did not have data on severity of RA for these patients. It is possible that the association with longer TTP may be with the severity of the disease rather than with RA itself, although it has been reported that fecundity is not associated with joint damage over time (10). We did consider the possibility that duration of RA (time since diagnosis) may influence TTP, since the disease may progress into more severe forms over time; however, within the subset of women with RA in our cohort, we did not find any correlation between RA duration and TTP (data not shown). This study has a number of limitations that should be recognized. First, data on RA diagnosis was available from the Danish National Hospital Discharge Registry, and it is possible that some of the women in our “no RA” group had been diagnosed with the disease outside the hospital system. Nonetheless, we do not expect to have many such misclassified cases. Second, we may have under-estimated the association between fecundity and RA since any women with RA who had planned a pregnancy but did not get pregnant would not be represented in our dataset. Third, although TTP data were collected after the end of the waiting time, and may have been subject to recall bias, we believe that any such misclassification will be small since the recall time was short and non-differential since this specific study was not mentioned at recruitment.D-Glucose In summary, our results show that women with RA had longer waiting time to pregnancy compared to those who did not have RA, indicating a slight reduction in fecundity.Etanercept Acknowledgments”The Danish National Research Foundation has established the Danish Epidemiology Science Centre that initiated and created the Danish National Birth Cohort.PMID:25804060 The cohort is furthermore a result of a major grant from this Foundation. Additional support for the Danish National Birth Cohort is obtained from the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Augustinus Foundation, and the Health F.
