premature infant
1. an infant usually born after the twentieth completed week and before full term, arbitrarily defined as one weighing 500 to 2499 grams at birth, having poor to good chance of survival, depending on the weight. In countries where adults are smaller than in the United States, the upper limit may be lower. Other criteria such as crown-heel length (less than 47 cm) and occipitofrontal diameter (less than 11.5 cm) have also been used. 2. preterm i.
Medical dictionary.
2011.