Contraction
A contraction was a muscular contraction of the uterine muscles. They commonly occurred during the late months of pregnancy, and were an indicator that labor was not far behind. (; )

When Deanna Troi was pregnant with Ian Andrew Troi, Jr. in 2365, Doctor Katherine Pulaski inquired as to how frequent her contractions were; Troi described them as "very close together." ()

Doctor Beverly Crusher was called to Sickbay by her nurse when Juarez' contractions were occurring one minute apart. ()

In 2378, Tom Paris gave  a hypo injection to speed up her contractions. ()

See also 
 False labor

External link 
 
Physiology
Sex and reproduction