the descent of the uterus into the pelvic cavity, occurring toward the end of pregnancy, changing the contour of the abdomen and facilitating breathing by lessening pressure under the diaphragm.
obstetrics the sensation, experienced by many women late in pregnancy when the head of the fetus enters the pelvis, of a reduction in pressure on the diaphragm, making it easier to breathe
lightening light·en·ing (līt'n-ĭng) n. The sensation of decreased abdominal distention during the latter weeks of pregnancy following the descent of the fetal head into the pelvic inlet.