To evaluate the natural history and pregnancy outcomes in fetuses with isolated polydactyly of upper limb diagnosed at 11-13 week scan. This was a retrospective study of 18430 pregnant women examined at 11 to 13+6 gestational weeks. In all studies both fetal hands were examined and fingers were counted either by transabdominal or transvaginal ultrasound. A total of 18430 patients were included in the study. The median maternal age was 29 years. The median Crown–rump length was 67 mm. Overall, we diagnosed 16 fetuses with isolated polydactyly, in 5 fetuses it was bilateral and 11 fetuses in was unilateral. Only one case of isolated unilateral polydactyly was missed at 11-13 week scan. In 4 fetuses with bilateral and 3 fetuses with unilateral polydactyly it was familial trait. In 4 cases of unilateral polydactyly there was spontaneous autoamputation of an extra digit between the 11-13 week scan and 20 week scan. In one of the fetuses with autoamputation of an extra digit there were additional ultrasound findings at 20 weeks scan suggestive for Trisomy 18 (inlet VSD and choroid plexus cysts). The diagnosis of Trisomy 18 was confirmed by amniocentesis. In other 15 fetuses there were no other findings at 20 weeks so there were no indication for fetal karyotyping. The newborns' examination revealed five normal fingers in all fetuses with autoamputation of an extra digit and these babies did not need any further surgical correction. In the rest 12 newborns the diagnosis of polydactyly was confirmed after birth and babies were operated at the age of 6-8 month. The vast majority of isolated polydactyly of the upper limb can be diagnosed at the time of 1st trimester ultrasound screening. A detailed fetal survey at a more advanced gestational age is mandatory, since some markers or fetal malformations may have a later manifestation. Autoamputaion of an extra digit during the first 20 weeks of pregnancy is not a rare finding but it doesn't exclude the presence of more severe fetal anomalies. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.