Abstract： This paper reports the diagnosis and treatment of a pregnant woman complicated with myotonic dystrophy (DM) type 1(DM1). The pregnant woman complained of occasional dull pain in the precardiac region accompanied by night sweats in the first trimester and a mild increase in myocardial enzymes was observed. Symptoms were improved after oral medication followed by no regular reexamination. While in the third trimester, abnormal myocardial enzyme, liver enzyme, and urinary protein were found and echocardiography and abdomen ultrasound suggested multiple organic lesions involving the heart and spleen. A girl was born through cesarean section at 36 +5 weeks of gestation due to maternal heart failure, with Apgar scores of 10 at 1 and 5 minutes. The patient developed acute respiratory failure, ventricular bigeminy, and diarrhea after surgery. Neurology consultation found incomplete buried eyelids in both eyes, weak bulging cheeks, and weak upper extremity muscle strength. Muscle biopsy confirmed the diagnosis of DM and genetic testing showed abnormal amplification of non-coding region [CTG] n in myotonic dystrophy protein kinase gene in chromosome 19q13.3, which indicated DM1. The mother recovered well at nine months postpartum. Further genetic analysis of pedigree and offspring is recommended.