At 25 weeks of fetal development, the baby measures about 13–14 inches long and weighs roughly 1.5–1.7 pounds. The body is becoming more proportionate as fat continues to accumulate beneath the skin, giving the fetus a slightly rounder appearance. The skin is still thin and wrinkled but gradually becoming smoother as growth continues. The lungs are developing steadily, with air sacs forming and increasing production of surfactant, which is essential for breathing after birth. While the lungs are