Page 30 - Fertility in Women with Rheumatoid Arthritis Vruchtbaarheid van vrouwen met reumatoïde artritis

Chapter 2
trying to conceive, or already pregnant. Teratogenic drugs, such as methotrexate (MTX), should have been stopped for at least 3 months.
Only patients included preconceptionally or during the rst trimester of pregnancy were eligible for the current analysis. If a patient participated twice or more, only the rst study episode was included.
Data collection
Patients were preferably visited before conception, during each trimester, and three times after delivery. Patients who did not conceive within 1 year after the rst visit were visited again 1 year later. At each visit, patients lled out questionnaires, were interviewed by a research team member, and provided details on variables possibly influencing fertility such as age, parity and smoking habits. Disease activity was measured and serum samples were stored at -80°C. Using a structured questionnaire, the researcher recorded the use, frequencies and dosages of anti-rheumatic medication. At the rst visit, the researcher recorded the date the patient rst began actively trying to conceive.
Patients who were already pregnant during the rst visit were asked when their last menstrual period had started. We calculated the TTP as the time elapsed between the rst attempt to conceive and the rst day of the last menstrual period before pregnancy. If the date of the last menstrual period was not known by the patient, this date was calculated by subtracting 280 days (40 weeks) from the due date based on sonographic examination during early pregnancy. In several cases the couple started to try for pregnancy after the start of the last menstrual period and succeeded within that rst month. To avoid negative values for the TTP, we calculated a ctitious date for the pregnancy test for all patients by adding 28 days to the start of the last menstrual period. These dates were used only in the univariate survival analyses and the Cox regression analyses.
Measurements
Disease activity scores were calculated using the 28-joint Disease Activity Score (DAS28) with three variables based on the C-reactive protein (CRP) level (mg/L).12 We categorised the disease activity scores according to the recommendations of the European League against Rheumatism (EULAR): in remission (DAS28≤2.6), low disease activity (2.6<DAS28≤3.2), intermediate disease activity (3.2<DAS28≤5.1) and high disease activity (DAS28>5.1).13
28