How Your Baby Is Growing and Developing Fetal growth is rapid now. As you can see in the illustration on page 103, the head is almost half the baby's entire length. External genitalia are beginning to show distinguishing features. Development of the fetus into a male or female is complete in another 3 weeks. If a miscarriage occurs after this point, it may be possible to tell if it is male or female.
All embryos begin life looking very much the same, as far as outward appearances are concerned.
Whether the embryo develops into a male or female is determined by the genetic information contained in the embryo. Some women notice changes in their hair, fingernails or toenails during pregnancy. This doesn't happen to everyone, but if it happens to you, don't worry about it. Some fortunate women notice an increase in hair and nail growth during pregnancy. Others find they lose some hair during this time.