What is lightening in terms of pregnancy?

Lightening refers to the process when the fetus descends into the pelvis as the body prepares for labor. This change typically occurs in the later stages of pregnancy, often a few weeks before labor begins. During lightening, the mother may notice that she can breathe more easily, as the pressure on her diaphragm is relieved; however, there may also be increased pressure on the bladder, leading to more frequent urination.

The other options describe different aspects of the labor and pregnancy experience but do not accurately capture the meaning of lightening. The onset of contractions is a separate event indicating that labor is beginning, a surge of energy can occur during the nesting phase, and increased fetal movements can happen throughout pregnancy without being specifically related to lightening. Thus, the correct answer accurately depicts the physical change occurring just before delivery.