Pregnancy Outcomes in Undifferentiated Connective Tissue Disease Compared to Systemic Lupus Erythematosus: A Single Academic Center's Experience

Systemic lupus erythematosus (SLE) patients have more pregnancy complications than healthy patients. Data regarding pregnancy outcomes in women with undifferentiated connective tissue disease (UCTD) are more limited, and existing studies are concentrated in Italy and predominantly in patients with a new diagnosis. Our objective was to compare pregnancy outcomes for UCTD and SLE patients with established disease.Between 2008 and 2017, patients with UCTD and SLE at an academic medical center were recruited to a prospective pregnancy registry. UCTD was defined as a positive autoantibody plus connective tissue disease symptoms not meeting criteria for another rheumatic diagnosis. SLE was defined by American College of Rheumatology or Systemic Lupus International Collaborating Clinics classification criteria or by physician diagnosis. Data were collected throughout pregnancy and postpartum. Comparator groups included UCTD, low-activity SLE, and high-activity SLE.A total of 150 SLE and 51 UCTD pregnancies were analyzed. Disease activity was low in most patients, although more patients with SLE had severe activity during pregnancy (12% versus 2%; P = 0.05). The frequencies of prematurity and preeclampsia were significantly lower in UCTD than in high-activity SLE patients (preterm 17% versus 45% [P = 0.004] and preeclampsia 6% versus 34% [P = 0.0008]), although similar to low-activity SLE patients. More infants who were small for gestational age were born to SLE than UCTD patients (33% versus 7% [P = 0.0005]), regardless of disease activity level.Pregnancies in women with UCTD managed by a rheumatologist have a high rate of pregnancy success and fewer risks than those in women with active SLE.