The long-term prognosis and genetic mechanism of pregnancy after intrauterine mosaic aneuploid blastocyst transfer remain unknown. We report the case of two babies after the aforementioned procedure and chromosomal analysis of their cord blood and chorionic villi. Case Report 1. A 41-year-old primipara, with two previous spontaneous abortions, was pregnant after intrauterine transfer of a blastocyst carrying 40% mosaicism of long-arm monosomy of chromosome 5. The amniocentesis results were 46,XX. A cesarean section was performed at 39 weeks. The female infant was 3,315 g at birth. Case Report 2. A 44-year-old primipara, with two spontaneous abortions, was pregnant after intrauterine transfer of a blastocyst carrying 40% mosaicism of long-arm monosomy of chromosome 9 and monosomy of chromosome 14. After genetic counselling, she decided not to undergo amniocentesis. No abnormalities were found by ultrasound. A cesarean section was performed at 38 weeks. The male infant was 3,340 g at birth. Chromosome analyses of postnatal cord blood and chorionic villi were performed using SNP arrays. The cord blood and chorionic villi showed no chromosomal structural abnormalities or mosaicism. For both, no disorders were observed at 10 months of age. We experienced the birth of babies after intrauterine transfer of mosaic aneuploid blastocysts.