Muscle contraction is the tightening, shortening, or lengthening of muscles when you do some activity. It can happen when you hold or pick up something, or when you stretch or exercise with weights.

When your water breaks, it means the amniotic sac has ruptured. This typically signals the beginning of labor, but it may be several hours before you feel a contraction. Share on Pinterest Eloisa ...

Braxton Hicks contractions are uterine contractions that start in early pregnancy. Most don't notice them until sometime in the second or third trimester – and some women never notice them at all.