A Case Report of Possible Superfetation with Evidence of Ult
Superfetation is when the second ovum is fertilized after there is already the 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 multiple pregnancies.

A 35-year-old gravida 1 para 0 presented to her OB/GYN at 7 weeks by known last menstrual period (LMP) for her first prenatal 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.