No one knows exactly what triggers real labor (and more women are concerned with “when” than”why”), but it’s believed that a combination of factors involved. This very intricate process begins the fetus, whose brain sets off a relay of chemical messages (which probably translate into something like, “Mom, let me out of here!” ) that kicks off a chain reaction of hormones in the mother. These hormonal changes in turn pave the way for the work of prostaglandins and oxytocin, substances that trigger contractions when all labor system are “go”.
You’ll know that the contractions of prelabor have been replaced by true labor if:
1. The contractions intensify, rather than ease up, with activity and aren’t relived by a change in positions.
2. Contractions become progressively more frequent and painful, and generally (but not always) more regular. Every contraction won’t necessarily be more painful or longer (they usually last about 30 to 70 seconds) than the last one,but the intensity does build up as a real labor progresses. Frequency doesn’t always increase in regular, perfectly even intervals, either- build it doesn’t increase.
3. Early contractions feel like gastrointestinal upset, or like heavy menstrual cramps, or like lower abdominal pressure. Pain may be just in the lower abdomen or in the lowest back and abdomen, and it may also radiate down into leg (particularly the upper thighs). Location, however, is not as reliable an indication, because false labor contractions may also be felt in these places.
4. You have show and it’s pinkish or blood-streaked.
In 15 percent of labors, the water breaks – in a gush or a trickle – before labor begins. But in many others, the membranes rupture spontaneously during labor, or are rupture artificially by the practitioner.