What are the characteristics of having a boy in the second trimester of pregnancy? The second trimester of pregnancy is approximately the 4th to 6th month of pregnancy. This period is the time when the fetus develops rapidly and is also the golden period for determining the gender of the fetus. Many expectant mothers hope that they can have a healthy baby and even want to know the gender of the fetus. There are many different characteristics and manifestations of being pregnant with a boy and being pregnant with a girl. Here are some aspects: