A new case of pregnancy in a 29-year-old woman with trisomy 21 is described. She gave birth to a male infant, chromosomally and phenotypically normal, who died the day after delivery due to prematurity. Thirty pregnancies of 26 affected mothers, including the present woman, resulted in 10 children with Down syndrome, 18 children (1 set of twins) without Down syndrome, and 3 spontaneous abortions. Although rare, pregnancies in women with Down syndrome could become more frequent, increasing the importance of genetic, reproductive, and obstetric problems. These problems are reviewed with special reference to the occurrence of nonspecific abnormalities in chromosomally normal children, difficulties in labor and delivery, and frequency of prematurity and low birth weight.