Level 1: Fetal size and weight at 38 weeks Fetal size and weight at 38 weeks of pregnancy are close to the final mature state. At this time, the average weight of the fetus is about 3.2 kilograms and the length is about 50 centimeters. However, every fetus grows and develops differently, so the size and weight of the fetus will also vary during this period. Level 2: Fetal organ development at 38 weeks of pregnancy. At 38 weeks of pregnancy, the fetal organs have basically completed development. At this point, their lungs are mature enough to breathe normally. At the same time, the heart, digestion,