Superfetation is a when second ovum is fertilized after there is already presence of an embryo in the uterine cavity. Human superfetation is extremely rare with less than 10 cases in the literature. According to previous research, the diagnosis of superfetation is suspected when there is a growth discrepancy in a multiple pregnancy. Case presentation: We present a case of a 35-year-old gravid 1 para 0 who presented to her OB/GYN at 7 weeks by known last menstrual period (LMP) for her first

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... tal visit. She was found to have single intrauterine pregnancy consistent with known LMP. At 12 weeks she had a cell free DNA (cfDNA) test performed that came back abnormal. The patient's next ultrasound at 19 weeks showed a twin gestation. Repeat cfDNA was normal for twin gestation and serial ultrasounds showed normal interval growth of both twins with the same discordance throughout the rest of the pregnancy. The cfDNA results, ultrasound findings demonstrating consistent growth discordance with normal interval growth otherwise, NICU management difference and placenta analysis post birth all support the diagnosis of superfetation. Discussion: This case adds to the literature of human Superfetation. Check for updates