31 weeks of pregnancy: Fetal development status and precautions 1. Fetal development At 31 weeks of pregnancy, the fetus has developed to half the size of a full-term baby, with a height of about 40 cm and a weight of about 1.5 kg. At this time, the fetus\’s skin is tough and smooth, its hair and eyebrows have grown, and its nails have grown and can be trimmed. The main organs of the fetus have been fully developed, and now the main task is to enhance the function of the organs. The fetal lungs and digestive system are basically