Braxton Hicks contractions are a normal part of pregnancy, described as a tightening sensation in the abdomen. They serve as “practice contractions,” preparing the uterus for labor without leading to cervical dilation. These contractions can begin as early as six weeks, though they are typically felt more noticeably in the second or third trimester. Their purpose includes toning uterine muscles and promoting blood flow to the placenta.
How Contraction Monitors Work
External contraction monitors, known as tocodynamometers or “tocos,” measure uterine activity. These monitors use a pressure-sensitive sensor placed on the pregnant person’s abdomen, held in place with a belt. The tocodynamometer detects changes in abdominal pressure as the uterus contracts. This pressure data is converted into a signal, displayed as a numerical reading in millimeters of mercury (mmHg) and a wave-like pattern on a monitor screen or printed strip. The monitor records the frequency and duration of these uterine tightenings, providing an objective measure of contraction patterns.
Braxton Hicks on the Monitor
Braxton Hicks contractions show up on a contraction monitor because the device registers any uterine tightening. Their appearance on the monitor’s tracing differs from true labor contractions. Braxton Hicks typically register as lower intensity contractions, often ranging between 5-25 mmHg. In contrast, active labor contractions are usually much stronger, often measuring between 40-60 mmHg, and can reach 50-80 mmHg during the second stage of labor.
The monitor tracing for Braxton Hicks shows an irregular pattern in frequency and duration. They do not consistently increase in strength, length, or how close together they occur. True labor contractions, conversely, display a pattern of progressively increasing intensity, becoming longer, and occurring with greater regularity and closer intervals on the monitor. The monitor solely detects uterine muscle activity and does not provide information about cervical changes, which are a defining feature of true labor.
Differentiating Contractions Without a Monitor
Distinguishing Braxton Hicks from true labor without a monitor involves observing several characteristics. Braxton Hicks are generally irregular in timing and do not follow a consistent pattern. They often vary in intensity and may subside or disappear with changes in activity, such as walking or resting, or by drinking water. Discomfort from Braxton Hicks is typically felt in the front of the abdomen and is more uncomfortable than painful.
True labor contractions, on the other hand, become more regular, frequent, and progressively stronger over time. They do not ease up with changes in position or activity. Pain from true labor often starts in the lower back and wraps around to the front of the abdomen, becoming intense enough to make talking or walking difficult. Each true labor contraction typically lasts between 30 to 70 seconds and consistently gets closer together.
When to Contact a Healthcare Provider
It is important to contact a healthcare provider if there are any concerns about contractions or other symptoms during pregnancy. Specific signs warranting immediate medical attention include regular, strong, or painful contractions, especially if they occur before 37 weeks of pregnancy. Other warning signs include any vaginal bleeding or bright red discharge, a sudden gush or continuous leaking of fluid, or a noticeable decrease in fetal movement. Persistent severe pain in the abdomen or back, or other symptoms such as fever, dizziness, or vision changes, also indicate the need for professional medical advice.