The sensation that a pregnant woman feels when the lowermost part of the fetus descends and is engaged in the mother's pelvis, an event that typically occurs 2 to 3 weeks before labor begins. Women who have had two or more prior viable pregnancies (multiparas) may not experience engagement until labor actually begins. When engagement occurs, there is a visible change in the shape of the woman's stomach because the baby drops lower in the abdomen. Also known as lightening because the pregnant woman feels lighter after this event. Most women feel more comfortable after engagement, but some may experience lower back pain as the fetus presses close to the tailbone and the sciatic nerve. Others may find movement more difficult due to the lower center of gravity caused by engagement.