The 4-month-old fetus is usually a little more than 16 weeks old, and the uterine fundus is usually between the umbilicus and the pubic symphysis at this time. At this time, the fetus is usually about 16cm long, with a top-rump length of about 12cm and a weight of about 110g. The sex of the fetus can be identified from the external genitalia, the scalp has grown very small hairs, and the fetus has started breathing movements. However, the skin of the fetus at this time is still relatively thin, usually dark red and basically without subcutaneous fat. Some pregnant women who are thinner and have thinner abdominal fat can already feel the fetal movement on their own.