Lightening

Not to be confused with a discharge of atmospheric electricity, lightening refers to the sensation that a pregnant woman feels when the baby drops. This is the time when the presenting (lowermost) part of the fetus descends into the maternal pelvis. Lightening classically occurs 2 to 3 weeks before labor begins. However, it may not occur in women who have had two or more prior viable pregnancies (and so are multiparas) until labor actually begins. Lightening is also called "engagement" because the presenting part of the fetus is then engaged in the mother's pelvis.

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Sensation of decreased abdominal distention during the later weeks of pregnancy following the descent of the fetal head into the pelvic inlet.

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light·en·ing 'līt-ən-iŋ, 'līt-niŋ n a sense of decreased weight and abdominal tension felt by a pregnant woman on descent of the fetus into the pelvic cavity prior to labor

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n.

the sensation experienced, usually after the 36th week of gestation, by many pregnant women, particularly those carrying their first child, as the presenting part of the fetus enters the pelvis. This reduces the pressure on the diaphragm and the woman notices that it is easier to breathe. Compare engagement.

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light·en·ing (lītґən-ing) the sensation of decreased abdominal distention produced by the descent of the uterus into the pelvic cavity, usually occurring from two to three weeks before labor begins.