Patient background.

Mixed connective tissue disease (MCTD) predominantly affects women in their reproductive age (30–40 years). This study is aimed to analyze a case series of MCTD-complicated pregnancies. The study design utilized a combined case-series and case–control approach. Pregnant women with MCTD were included and categorized into two groups: the live-birth and non-live birth (encompassing miscarriages at <12 weeks and stillbirths at ≥12 weeks) groups. Primary outcomes included delivery outcomes and factors associated with live births. A total of 57 pregnancies from 34 mothers (median age: 33.0 years) were included. Regarding delivery outcomes, the rates for live birth, miscarriage, and stillbirth were 64.9, 29.8, and 5.3%, respectively. Additionally, the respective rates of preterm delivery, fetal growth restriction (FGR), and small-for-gestational-age (SGA) were 18.9, 18.9, and 27.0%. Higher steroid usage (62.2 vs. 30.0%, p = 0.02) and lower prednisolone dosage in the live birth group (median dose: 7 vs. 10 mg, p = 0.03) were found to be significant factors contributing to live births. MCTD during pregnancy was associated with increased risks of miscarriage, stillbirth, preterm delivery, FGR, and SGA. Notably, low-dose steroid therapy was identified as a contributing factor to successful live births.