During childbirth, a woman can experience motions in the uterus known as uterine contractions. These powerful, painful movements are a part of the childbirth process. They can also occur at other times, such as during menstruation and female orgasms.
Contractions have a variety of purposes during labor. They help release the hormone oxytocin into the mother's body, which helps her to dispense the milk needed to feed her baby. Breastfeeding itself can cause the uterus to contract, allowing it to shrink back to its normal pre-pregnancy size. Oxytocin may also help trigger maternal behaviors, as well as bonding between the mother and baby.
Uterine contractions also assist the cervix in thinning and dilating during childbirth, allowing for the delivery of the baby. Postpartum contractions help the uterus clot, aiding in the prevention of possible blood loss. The contractions also assist the infant in descending into the birth canal for delivery.
The pain produced by contractions depends on their strength and length. When labor begins, contractions are generally considered mildly painful. As labor progresses during a delivery, they typically become longer, as well as moderately to severely painful. This is particularly true during transition labor, which often produces intense pain.
Early uterine contractions may be the result of false labor, and these are known as Braxton Hicks contractions. Named by English physician John Braxton Hicks, these intermittent spasms may start as early as the sixth week of pregnancy, though they are generally not felt until the second or third trimester. Unlike labor pains, these are painless and irregular, and they are thought to prepare a woman for her baby's delivery.
Women may also experience these spasms during their menstruation, too. Though menstrual cramps are usually considered considerably less painful than labor ones, they can cause notable pain or discomfort. Some women find relief through exercise, using a heating pad or hot water bottle, or through other natural means. Several medications are also available to help remedy this pain. Women with more intense symptoms and recurring pain may need to see a gynecologist for treatment.
Sexual intercourse can also induce contractions in the uterus. During female orgasm, the vagina and uterus contract to support the transport of male semen to the fallopian tubes. Though these contractions are not always felt, they can occasionally be painful. Those during orgasm are more likely to be felt by pregnant women in late stages of pregnancy.