We describe the first case of a baby with maternal uniparental disomy of chromosome 2. Growth failure, hypothyroidism, and hyaline membrane disease were present at birth, and the first year of life was complicated by bronchopulmonary dysplasia. At age 14 months, motor and intellectual development were normal, but growth remained below the 10th centile. The baby was investigated for uniparental disomy because trisomy 2 mosaicism had been detected in a second trimester amniocentesis. This is the first reported case in which amniotic fluid chromosome mosaicism has been associated with uniparental disomy. Implications for prenatal diagnosis are considered.