Objectives To evaluate whether pregnancy is a risk factor for the onset of SLE in women of the reproductive age.
Methods Female patients who had first onset of SLE during pregnancy between the age of 15 and 49 years were identified from our SLE cohort database (year 1999-2013). The incidence of SLE during pregnancy in women of the reproductive age was calculated by the ratio of pregnancy-onset SLE and the total number of obstetric deliveries in our hospital within the same study period (data retrieved from the obstetric registry). The observed incidence of SLE onset during pregnancy was compared with the expected incidence of SLE in women of the reproductive age (age 15-49 years) in the general population (data retrieved from a clinical registry of all public hospitals in Hong Kong using the diagnostic codes of SLE and its related complications, and the population census data in the years 2001, 2006 and 2011) by the Chi-square test (95% asymptotic confidence intervals calculated). The clinical presentations, course and prognosis of pregnancy-onset SLE were compared with other non-pregnancy-onset female SLE patients.
Results 742 female SLE patients were in our cohort; 15 patients had first onset of SLE during their pregnancies (age of onset 29.5±5.3 years; 13% in first trimester, 47% in second trimester, 40% in third trimester). Compared to non-pregnancy-onset female SLE patients (N=727), there were more renal disease, thrombocytopenia and central nervous system involvement as initial manifestations of pregnancy-onset SLE. Three (20%) patients also qualified the diagnosis of the obstetric antiphospholipid syndrome. Fetal outcome was poor in patients with onset of SLE during pregnancy: intrauterine death (13%), spontaneous or therapeutic abortion (33%) and preterm delivery (13%). The maternal prognosis of pregnancy-onset SLE, however, was generally good, with good response to treatment and very infrequent disease flares on follow-up. The SDI damage score was significantly lower in pregnancy-onset than non-pregnancy-onset SLE patients (0.33±0.49 vs 1.09±1.6; p<0.001). There was no mortality in pregnancy-onset SLE patients (compared to 11.4% in the remaining cohort). The total number of deliveries registered in our hospital in women of the age 15-49 years between 1999 and 2013 was 71224. The observed incidence of SLE during pregnancy was 0.014/1000 person-year. During the same time period, the incidence of new onset SLE in all public hospitals in Hong Kong relative to the mean female population (15-49 years of age) from 1999 to 2013 was 0.077/1000 person-year. The odds ratio (OR) of having new onset SLE during pregnancy was 0.22 (95%CI 0.13-0.39; p<0.001).
Conclusions In women of the reproductive age, pregnancy protects against the development of SLE. First onset of SLE during pregnancy often leads to poor fetal outcome. However, the maternal outcome of pregnancy-onset SLE is generally good, with good response to treatment, infrequent relapse of organ manifestations and smaller risk of organ damage in the long run.
Disclosure of Interest None declared