The phrase “water breaks” is the common description for the medical term “rupture of membranes“. So the answer to the question – what does it mean when your water breaks — is that your amniotic sac has ruptured and amniotic fluid is leaking from your body.
Although research on the role of amniotic fluid is still ongoing, a well-cited 2005 research article notes that:
“Amniotic fluid is a wonderfully complex and unique body fluid that nourishes and protects the fetus. Just as breast milk is the optimum beverage for the newborn, amniotic fluid is the ideal, germ-free bath, cushion and liquor for the fetus.”
Amniotic fluid is different than urine. Since leaking urine during late pregnancy is common, doctors use a simple test to distinguish leaking of amniotic fluid from leaking of urine. The American College of Obstetricians and Gynecologists notes that “most women go into labor within hours of their water breaking.” Most sources recommend that you should go to the hospital immediately after your water breaks to minimize infection risk for your baby.
As I wrote in the post about my baby’s birth, my wife’s water broke when she was 38 weeks pregnant. In our case, her water breaking was not a sign that she was going into imminent labor. My wife was only slightly dilated when we arrived at the hospital, but the staff admitted us immediately after they confirmed that her water had broken. It took more than 24 hours in the hospital and augmentation with a synthetic hormone called Pitocin for actual labor to begin.
Although most people think having your water break is synonymous with going into labor, most doctors describe the period as pre-labor or early labor. Many women have an experience similar to my wife whereby it takes hours for the cervix to dilate enough to begin actual labor.