Braxton Hicks Contractions

Etiology

Braxton Hicks contractions are caused when the muscle fibers in the uterus tighten and relax. The exact etiology of Braxton Hicks contractions is unknown. However, there are known circumstances that trigger Braxton Hicks contractions including when the woman is very active, when the bladder is full, following sexual activity, and when the woman is dehydrated. A commonality among all these triggers is the potential for stress to the fetus, and the need for increased blood flow to the placenta to provide fetal oxygenation.[4][5][6]

Epidemiology

Braxton Hicks contractions are present in all pregnancies. However, each woman's experience is different. Most women become aware of Braxton Hicks contractions in the third trimester, and some women are aware of them as early as the second trimester. Sometimes Braxton Hick contractions occurring near the end of the third trimester of pregnancy are mistaken as the onset of true labor. It is not unusual, especially in a first pregnancy, for a woman to think she is in labor only to be told it is Braxton Hicks contractions and not true labor.

Pathophysiology

Braxton Hicks contractions are thought to play a role in toning the uterine muscle in preparation for the birth process. Sometimes Braxton Hicks contractions are referred to as "practice for labor." Braxton Hicks contractions do not result in dilation of the cervix but may have a role in cervical softening.

The intermittent contraction of the uterine muscle may also play a role in promoting blood flow to the placenta. Oxygen-rich blood fills the intervillous spaces of the uterus where the pressure is relatively low. The presence of Braxton Hicks contractions causes the blood to flow up to the chorionic plate on the fetal side of the placenta. From there the oxygen-rich blood enters the fetal circulation.

History and Physical

When assessing a woman for the presence of Braxton Hicks contractions, there are some key questions to ask. Her response to these questions will assist the healthcare provider to differentiate Braxton Hicks contractions and true labor contractions.[7][8][9]

• How often are the contractions? Braxton Hicks contractions are irregular and do not get closer together over time. True labor contractions come at regular intervals, and as time goes on, they get closer together and stronger.
• How long are the contractions? Braxton Hicks contractions are unpredictable. They may last less than 30 seconds or up to 2 minutes. True labor contractions last between 30 to less than 90 seconds and become longer over time.
• How strong are the contractions? Braxton Hicks contractions are usually weak and either stay the same or become weaker and then disappear. True labor contractions get stronger over time.
• Where are the contractions felt? Braxton Hicks contractions are often only felt in the front of the abdomen or one specific area. True labor contractions start in the midback and wrap around the abdomen towards the midline.
• Do the contractions change with movement? Braxton Hicks contractions may stop with a change in activity level or as the woman changes position. If she can sleep through the contraction, it is a Braxton Hicks contraction. True labor contractions continue and may even become stronger with movement or position change.

During the physical assessment, the provider may palpate an area of tightening or a "spasm" of the uterine muscle, but the presence of a uterine contraction in the uterine fundus is not palpable. The woman will be assessed for the presence of uterine bleeding or rupture of the amniotic membrane. An examination of the cervix reveals no change in effacement or dilatation as a result of the Braxton Hicks contractions.

Evaluation

There are no laboratory or radiographic tests to diagnose Braxton Hicks contractions. Evaluation of the presence of Braxton Hicks contractions is based on an assessment of the pregnant woman's abdomen, specifically palpating the contractions.

Treatment / Management

By the midpoint of pregnancy, the woman and provider should discuss what the woman may experience during the remainder of the pregnancy. Braxton Hicks contractions are one of the normal events a woman may experience. Teaching her about Braxton Hicks contractions will help her to be informed and to decrease her anxiety if they occur.[10][11][12]

There is no medical treatment for Braxton Hicks contractions. However, taking action to change the situation that triggered the Braxton Hicks contractions is warranted. Some actions to ease Braxton Hicks contractions include:

• Changing position or activity level: if the woman has been very active, lie down; if the woman has been sitting for an extended time, go for a walk.
• Relaxing: take a warm bath, get a massage, read a book, listen to music, or take a nap.
• Drinking water to rehydrate.

If these actions do not lessen the Braxton Hicks contractions or if the contractions continue and are becoming more frequent or more intense, the patient's healthcare provider should be contacted.

Also, if any of the following are present the healthcare provider should be contacted immediately:

• Vaginal bleeding
• Leaking of fluid from the vagina
• Strong contractions every 5-minutes for an hour
• Contractions that the woman is unable to "walk through"
• A noticeable change in fetal movement, or if there are less than ten movements every 2 hours.

Differential Diagnosis

• Abdominal distention

• Amenorrhea

• Ascites

• Full bladder

• Hematometra

• Nausea

• Ovarian cysts

• Pseudocyesis

• Uterine fibroids

• Vomiting