Level 1: Characteristics of a male fetus at four months of pregnancy. At four months of pregnancy, if the fetus is male, its reproductive organs have been fully formed and can be confirmed by B-ultrasound. In addition, male fetuses have wider heads, shoulders, and necks than female fetuses, and are relatively larger. In addition, the heart rate of male fetuses is slightly lower than that of female fetuses. Level 2: The development of the male fetus at four months of pregnancy is