The          period begins 8weeks after fertilization (10 weeks after the LNMP) and ends at birth.

It is characterized by rapid body growth and differentiation of tissues and organ systems.

An obvious change in the fetal period is the relative              of head growth compared with that of the rest of the body.

At the beginning of the 20^th week,           (fine downy hair) and head hair appear and the skin is coated with              (a fatty cheesy substance).

The eyelids are closed during most of the fetal period, but they begin to reopen at approximately 26weeks.

At this time, the fetus is usually capable of                       , mainly because of the maturity of its respiratory system.

Up to 30weeks, the fetus appears reddish and wizened(wrinkled) because of the thinness of its skin and the relative absence of subcutaneous fat.

       usually develops rapidly at 26 to 29 weeks, giving the fetus a smooth, healthy appearance.

The fetus is less vulnerable to the                  effects of drugs, viruses, and radiation, but

these agents may interfere with growth and normal functional development, especially of the            and            .

The physician can determine whether a fetus has a particular disease or birth defect by using various diagnostic techniques, such as amniocentesis(CVS),                   , and        .

In selected cases, treatments can be given to the fetus, such as drugs to correct              or thyroid disorders. Surgical correction of some birth defects in            is also possible. (e,g, ureters that do not open into the bladder can be surgically corrected).