Pregnancies complicated by trisomy 13 (T13) or trisomy 18 (T18) present unique challenges for obstetric management. From the initial diagnosis, the task of counseling these women and families is difficult because fetal and neonatal outcomes vary depending on the phenotype and degree of intervention chosen by the family. A literature review was performed using PubMed to gather information regarding obstetric management and outcomes of pregnancies complicated by T13 and T18. Spontaneous abortion and in uterofetal demise occur at rates well above those seen in chromosomally normal pregnancies. In addition, infants with T13 or T18 frequently have structural anomalies, which lead to worse prognoses and long-term survival. In cases in which a woman and her family desire to continue the pregnancy, multidisciplinary consultation with obstetrics, social work, genetics, and pediatrics can optimize care of both the fetus and the mother. Most commonly, prenatal care does not differ from routine. A detailed delivery plan should be generated, specifically discussing interventions for the patient and her fetus. When managing pregnancies complicated by T13 and T18, active, open, and frequent communication between the patient, her family, and a multidisciplinary health care team throughout the pregnancy is crucial.