Braxton Hicks and prelabor
Labor is actually a progressive action that begins slowly during the ninth month and then gathers speed.
After months of relative inactivity, the uterus contracts more and more often in the weeks before birth. Occasional uterine contractions have taken place throughout pregnancy, but they have been so sporadic and weak that they have had no effect on the cervix.
Contractions during the ninth month still tend to be brief, irregular, and imperceptible to the mother, but they are more frequent and coordinated than earlier ones.
These contractions were first described by an English doctor named John Braxton. Hicks in 1872, and hence they became known by his name. During the last several weeks of pregnancy they increase tremendously in frequency and may even become somewhat rhythmic. The period in which this happens is called prelabor.
Prelabor contractions work toward shortening (effacing) and widening (dilate) the tube-shaped cervix and stretching the bottom of the uterus.
The contractions also soften the cervix. This process is called ripening; it indicates that the cervix is becoming ready for labor. The "lip-soft" cervix of pregnancy now becomes "pudding-soft." Thus women enter labor with varying amounts of the work of delivery already done in prelabor.
By the final weeks of pregnancy, many women have dilated their cervix about two centimeters and have thinned and shortened it between 20 and 60 percent.
Is it "false" labor?
If Braxton Hicks contractions increase and become rhythmic late in the pregnancy, they are referred to as "false labor." What distinguishes false labor from real labor is simply that after a point, false labor does not progress and it eventually stops. The determination of whether labor is false can only be made in retrospect, there is still no test that can distinguish it from real labor. Many obstetricians and midwives say there is actually no difference between the two.
Not only are the types of contractions indistinguishable, they serve the same purpose; that is, they prepare the cervix and the uterus for delivery.