Why Do Braxton Hicks Contractions Occur?

Pregnancy brings a wide range of symptoms, some more pleasant than others. By the time the end of the third trimester rolls around, the baby is big enough to start causing plenty of aches in both the lower back and pelvic area while also pushing your uterus up into your diaphragm and rib cage, leading to shortness of breath and indigestion, as per the Mayo Clinic. Heartburn, feeling a frequent need to urinate, and hemorrhoids round out the symptoms as pregnancy comes to a close. But this just sums up the physical experience — there is also an emotional component to the end of pregnancy, in which feelings of fear and anxiety tend to come up around labor, birth, and the transition to parenthood.

As you put the finishing touches on your baby's nursery and finalize their name, your body will be busy preparing for the upcoming Herculean feat that is labor. The Cleveland Clinic points out that there are some pre-labor signs that you can keep an eye out for in those final weeks, including diarrhea, backaches, and the loss of the mucus plug, which is exactly what it sounds like — a glob of mucus that has been sealing the opening of your cervix during the entire pregnancy to protect the baby from potentially harmful bacteria.

One more way the body prepares for labor is with the practice of uterine contractions, known as Braxton Hicks (via Cleveland Clinic).

Braxton Hicks contractions act as a test run for labor

Braxton Hicks contractions are also referred to as false labor contractions because they aren't the type of contractions that the uterus undergoes when actually expelling the baby from the body, per WebMD. They don't indicate that labor is imminent but rather allow the uterus to practice contracting in the weeks leading up to birth. Unlike true labor contractions, they are also rarely painful, although they can cause some discomfort, and are marked by belly tightening and an irregular pattern of occurrence. They also tend to disappear if you change position or drink water. While Braxton Hicks contractions are common and completely normal, not everyone gets them.

It is not definitively known why Braxton Hicks contractions occur but doctors believe that they assist in the softening of the cervix, which is a necessary precursor to the baby moving through the birth canal, explains the Cleveland Clinic. During the days and weeks leading up to birth, the cervix must flatten out, a process known as effacement, to then allow for dilation, which is when the cervix opens to accommodate the baby passing out of the uterus and into the vagina, also per the Cleveland Clinic. The contraction of the uterine muscles pushes the baby's head against the cervix, aiding in the effacement and dilation process. The Mayo Clinic Health System adds that Braxton Hicks contractions also tone the uterus, making it strong for when it comes time to move the baby out.

How to tell if it's Braxton Hicks or true labor

For some people, it can be understandably difficult to tell the difference between a Braxton Hicks contraction and the onset of true labor, especially as the baby's due date gets closer. As a general rule, Braxton Hicks contractions won't increase in frequency or intensity over time and will disappear with a change in activity on your part, explains Healthline. They will last for less than two minutes and involve a tightening sensation in the front of the belly, but won't cause pain.

You'll know your body is actually going into labor when you experience contractions that are painful and get increasingly more painful over time. They will occur in waves lasting from half a minute to just over a minute and involve a distinct pattern. Over time, these contractions will move closer together and won't go away if you change position or activity.

March of Dimes adds that you can tell your contractions are a sign of real labor when they're accompanied by other symptoms as well, including the rupture of amniotic fluid, also known as the water breaking, and the presence of the bloody show, which is vaginal discharge tinged with blood. The key to knowing for sure whether the baby is coming or not is to time your contractions. In fact, when contractions last for one minute every five minutes for more than two hours, you should head to the hospital (per UC San Diego Health).