At 25 weeks of gestation the fetus reaches a length of 32 cm, the weight is increased to 700 g, head diameter is 62.3 mm, the diameter of the chest – 63.1 mm, tummy – 64.2 mm.
The skin of the baby becomes less wrinkled, more supple and bright. The brown fat accumulated in the subcutaneous tissue gives some roundness to the cheeks. The folds appear on the arms and legs. The auricles of the child are soft and thin, the cartilage which forms their foundation, is not yet sufficiently developed, curls and twists are not yet fully formed. The density of the cartilage of ears is included in the list of criteria for a full-term fetus, as the ears are judged on the development of the child, in case of its premature birth.
The surfactant continues accumulating in the lungs of the baby. It began to form in the lungs of the child at the 23th week of pregnancy. Surfactant prevents the decay of the lungs after first inhalation of the newborn. However, such babies born at 25 weeks have still small enough chances to breathe on their own. Most often, at such extent of prematurity observed the respiratory system of a child failure requiring mechanical ventilation. Also the number of alveoli in the future baby increases.
On the twenty-fifth week the fetus’s heart beats with a frequency of 140-150 beats per minute, and the doctor can hear it using obstetric stethoscope.