Page 90 - Fertility in Women with Rheumatoid Arthritis Vruchtbaarheid van vrouwen met reumatoïde artritis

Chapter 6
variables with AMH levels were tested separately using linear multiple regression on the log-transformed AMH values. A multivariable analysis was performed by entering all variables of interest into the multiple linear regression. Since AMH can be considered a proxy for ovarian age despite a woman’s calendar age, the multivariable analysis was performed both with and without age as a covariate.
To study the TTP, a Kaplan-Meier curve was drawn. To avoid negative values of TTP for women who conceived within the rst menstrual cycle, the ctitious date of the positive pregnancy test was calculated by adding 28 days to the rst day of the nal menstrual period. The Cox proportional hazard analysis was performed with the occurrence of pregnancy as event variable. Aside from log-transformed AMH levels and age, covariables were selected on the basis of our previous study on TTP in RA: never been pregnant before, disease duration, presence of RF and ACPA, DAS28, preconceptional use of NSAIDs, of prednisone and of sulfasalazine, and past methotrexate use. Smoking was not included, since the percentage of smokers in the PARA study was low and had no effect on TTP in the previous study.2 Presence of erosions was added, as a measure for long term disease severity. In a second analysis, age was excluded, to study whether unadjusted AMH levels showed an association with TTP.
P-values below 0.05 were considered statistically signi cant. Statistical software used is STATA 14.1 (College Station, Texas, USA).
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