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Uterine Contractions - Types, Signs, and Implications

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Uterine contractions refer to the tightening and compaction of the uterine muscles. They occur in both a non-pregnant and a pregnant uterus.

Medically reviewed by

Dr. Richa Agarwal

Published At February 17, 2023
Reviewed AtFebruary 17, 2023

Introduction:

The uterus is a female reproductive organ that provides protection and nutritional support to the ovum from fertilization until it develops into a fetus. A muscle layer in the middle region of the uterus, known as the myometrium, is responsible for uterine contractions.

Which Hormone Stimulates Uterine Contractions?

An endogenous (produced inside an organism) hormone called oxytocin stimulates uterine contractions for childbirth. During the labor process, when the fetus's head is pushed against the cervix, the nerve impulses from the stimulation travel to the brain and stimulate the pituitary gland to release oxytocin into the bloodstream. The oxytocin then travels to the uterus, and contractions begin. These contractions cause the pituitary gland to release more oxytocin, increasing the frequency and intensity of contractions. Oxytocin then increases the production of prostaglandins (a lipid group with actions like hormones), which moves the labor along and induces more contractions. This, in turn, carries out the vaginal delivery ultimately.

What Are the Different Types of Uterine Contractions?

Uterine contractions occur during the regular menstruation cycle and are called menstrual cramps. Rhythmic contractions occur in the myometrium leading to endometrial waves in a nonpregnant uterus. Uterine contractions that occur during labor are regular and painful. In addition, they cause the cervix to be thin and open, helping the baby descend into the birth canal. The different types of contractions in labor are:

1. False Labor - By the fourth month of pregnancy, the uterus contracts from time to time. This tightening or contraction is known as a Braxton Hicks contraction. A Braxton Hicks contraction occurs irregularly and in an infrequent manner. They both get long, strong, and close together. They also do not cause any changes in the cervix. These contractions can occur in case of dehydration, prolonged standing, or when tired. It usually eases up when the particular cause is removed, like getting hydrated in case of dehydration or sitting after standing for long periods.

2. Preterm Labor Contractions - Contractions that occur before 37 weeks are signs of preterm labor. Preterm contractions occur in a regular pattern; a contraction can be felt every 10 to 12 minutes for over an hour. During contractions, the entire abdomen gets hard to the touch. Some risk factors associated with preterm labor are multiple pregnancies, high-stress levels, infections, being underweight or overweight before pregnancy, smoking or drug abuse, and abnormal conditions of the cervix, uterus, or placenta.

  • True Labor Contractions - Once true labor contractions start, they get stronger, longer, and closer together. True labor contractions work to dilate the cervix. The stages of actual labor are:

  • Early Labor - Contractions in the early labor stage are mild. The contractions are felt from 30 to 90 seconds. These contractions are organized and occur at regular intervals. They can be spaced far apart but become close to five minutes by the end of early labor. During early labor, the water breaks, a sign that the labor is beginning.

  • Active Labor and Transition - The transition phase is when the cervix opens to provide the exit pathway to the baby. Contractions leading the transition phase are stronger than those experienced in the early labor stage. During this stage, the cervix opens from around 4 to 10 cm before the baby exits. Active labor contractions last from 45 to 60 seconds, with rest between three to five minutes. In the transition phase, the cervix dilates from around 7 to 10 centimeters, and the pattern of contractions lasts from 60 to 90 seconds, with 30 seconds to 2 minutes of rest in between.

When Do True Labor Contractions Start, and What Do Uterine Contractions in True Labor Feel Like?

For most women,

Real labor contractions begin after the 37th week of pregnancy. Contractions in true labor occur in a wave pattern. They are wrapped around the body, beginning from the back and moving around the torso to the abdomen. Leg cramping and ache may also occur. The pain starts slowly, rises until it peaks, and finally goes away. The uterine contractions last from about 30 to 70 seconds.

When Do Premature Labor Contractions Start, and What Are the Signs of Uterine Contractions in Preterm Labor?

In premature labor, real labor contractions begin before the 37th week of pregnancy. In preterm labor contraction, a sensation of tightening in the uterus is associated with a dull backache, pressure in the pelvic and abdominal region, and cramping.

When Do Braxton Hicks Start, and What Do Braxton Hicks Feel Like?

Braxton Hicks begins to form in the third trimester of pregnancy. They are uncomfortable, painless, mainly concentrated in the abdomen, and make the belly feel tight. The contractions last from less than 30 seconds to 2 minutes.

What Are the Common Complaints That Come With Uterine Contractions in Active Labor?

Some of the most common complaints that come with active labor contractions are:

  • Nausea.

  • Lightheadedness.

  • Vomiting.

  • Chills.

  • Hot flashes.

How Can Uterine Contractions Be Timed?

Uterine contractions can be timed by their frequency and length.

  • Frequency - To measure the frequency of the contractions, use a watch or clock, and note the time from when one contraction begins to the beginning of the next contraction. True labor contractions present a regular pattern of contractions, and the contractions grow closer together. In case of false labor, irregular contractions are observed.

  • Length of the Contraction - The length of each contraction should be noted, from when it begins until when it stops. True contractions last about 30 seconds from the onset and progressively get longer and stronger up to 75 seconds. In the case of false labor, their contractions vary in intensity and length.

How Can an Active Labor Contraction Be Confirmed, and When to Head to the Hospital?

The active labor contractions follow a pattern. The contractions are frequent with or without pain. They can accompany pain and bleeding. Water-like fluid (fluid inside the amniotic sac) may break, leading to fluid leaking from the vagina. Immediately rush to the hospital if the contractions are closer than five minutes apart.

Do Uterine Contractions Occur After Birth?

Yes, uterine contractions do occur after birth. However, they are normal and occur commonly among most women. During the postpartum period, the uterus shrinks back to its size with these contractions. The contractions also compress blood vessels in the region where the placenta is attached, thereby preventing postpartum hemorrhage. These contractions can be felt like short sharp cramps in the abdomen region, like a labor contraction or a menstrual cramp. The contractions usually decrease their intensity with each day during the postpartum period.

Conclusion:

Uterine contractions are muscle contractions in the uterus aiding childbirth. Understanding the difference between false and true labor, recognizing the signs of a true labor contraction, and noting the time between each contraction and the length of contractions is essential. If contractions occur closer than five minutes and last for about a minute, it denotes active labor; visit the nearest hospital immediately.

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Dr. Richa Agarwal
Dr. Richa Agarwal

Obstetrics and Gynecology

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uterine disorders
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