A vanishing twin (VT), also known as fetal resorption or disappearing twin syndrome, is a phenomenon that occurs in multiple pregnancies where one fetus dies and is partially or completely absorbed. This typically happens early in pregnancy, often before the woman is even aware that she is pregnant with twins. The surviving twin continues to develop normally, while the deceased twin may be reabsorbed by the body or may remain in the womb and eventually be expelled during birth as a fetus papyraceus. This event is most often documented in pregnancies obtained by ART, due to the multiplication of ultrasound examinations in early pregnancy. The incidence of VT appears to account for almost 20% of first-trimester twin pregnancies. The pathophysiology of VT is poorly understood, but one cogent hypothesis is that of an unbalanced and discordant chromosomal abnormality underlying spontaneous selective embryonic arrest. The existence of VT is likely to interfere with prenatal screening for trisomy 21 (screening by serum markers or cfDNA test). Similarly, several studies suggest that VT may increase the risk of prematurity or low birth weight. Screening for VT is essential, as it has a clear impact on the screening for chromosomal abnormalities and a possible impact on obstetric outcomes. However, these risks remain lower than in the case of progressing twin pregnancies.