A range of natural biological changes take place in a woman’s body during pregnancy, which directly affects the musculoskeletal system and may become a potential cause of back pain and related issues, such as leg pain.
Pregnancy-related changes typically involve the joints and connective tissues, making them loose, pliable, and soft. These changes result in increased stress and strain on the spinal and pelvic joints in the lower back and hips. Back pain may develop as early as the first trimester and typically increases as pregnancy continues.1
The pain can vary from intermittently minor discomfort, to chronic and debilitating. The pain may originate in the mid and/or lower back area and typically includes the pelvis and hips. The lumbar spine (lower back) and sacroiliac joints are most commonly affected due to changes in posture, joint stability, body weight, and shape.2
While in most cases back pain is self-limiting, resolves after delivery, and does not cause lasting issues,3 some women may continue to be affected by pain in the lumbar and/or pelvic region for several months or years.4 In general, women who receive postural and activity-related counseling during pregnancy are less likely to develop severe back pain symptoms.
This article describes the causes and types of pregnancy-related lower back pain in detail, including insights on treatment options and the occurrence of back pain after birth.
Typical Features of Lower Back Pain in Pregnancy
Back pain affects over 50% of pregnant women. While it can occur at any time during pregnancy, back pain is usually most troublesome during the second and third trimesters.5-7 Pregnancy-related symptoms and signs affecting the lower back typically result in reduced overall function and include (but are not limited to)5:
- Pain of varying intensity that starts or flares during movement or activity, such as while sitting, standing, walking, lifting objects, sexual intercourse, bending, and/or twisting the spin
- Sleep disturbances due to pain while turning in bed, lack of sleep, and reduced sleep hours
- Reduced range of motion in the lower back (lumbar spine)
- Changes in balance and walking patterns, especially in the second and third trimesters
These changes mostly occur due to the shift in the center of gravity towards the abdomen. This shift increases the curve of the lower spine and causes a slight backward tilt of the sacrum (part of the spine that connects the lower back to the hip).5
The effect of activity and weight on back pain
While pregnant women who lead a sedentary lifestyle may be at a higher risk of developing back pain, engaging in heavy physical labor or being active through the day may also lead to back pain symptoms in pregnancy.3
Limited research indicates that women with increased body mass index (BMI) may be at a higher risk of developing back pain while pregnant.3
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Average Duration of Lower Back Pain in Pregnancy
Research indicates that over half the population of pregnant women experience pain in the lower back and/or pelvic region lasting more than 3 months, typically during the second and/or third trimester.5
- A small percentage of women may experience pain as early as 4 to 16 weeks.5
- The fifth to seventh month period typically has the highest reports for pregnancy-related back pain.5
- Up to 10% of women may have pain through all the 3 trimesters of pregnancy.5
Back pain that continues after delivery is called postpartum back pain. About 72% of women continue to experience postpartum pain in the lower back and pelvis up to 1 year after delivery, which may extend up to several years in some cases.5
When Back Pain Is an Early Sign of Pregnancy
Since only a fraction of women develop back pain during the very early stages of pregnancy,3 the symptom is not usually identifiable as a sole or significant indicator of gestation. When back pain is accompanied by other symptoms and signs, such as a missed period, morning sickness, constant nausea, fatigue, and/or body soreness, it may indicate early pregnancy.
How Pregnancy-Related Changes May Cause Back Pain
Women usually gain between 20lb to 25lb (on average) during pregnancy, have a shift in their point of gravity, and undergo several hormonal and anatomical changes. These natural alterations increase stresses and loads on the lower spine and pelvis, contributing to the following changes:
- Modifications in posture. The growing uterus and increased curvature of the lower spine exert additional mechanical loads on the lower back, altering the spinal posture. This altered posture increases stress on the lumbar facet joints and lumbar spinal discs.8 Pelvic rotation occurs at the second sacral segment (S2-S3), which increases as the curve in the lumbar spine becomes more pronounced.1
- Changes in muscle tone and balance. The paraspinal muscles, which support and stabilize the lower back, shorten, and become unbalanced by the excessive stretching of the abdominal muscles in the front.
- Discomfort in the sacroiliac joints. A 10-fold increase in the concentration of the relaxin hormone during pregnancy causes softening of connective tissue in the pelvis and lower back, which leads to discomfort in the sacroiliac joints.3
- Stress on the pelvic joint. The pelvis is a stabilizing structure in the lower body that transfers loads from the upper body to the legs. Hormonal changes, alterations in posture and walking pattern, and stress on ligament structures may cause increased forces across the pelvic joints in pregnant women. Pregnancy-related changes cause an impaired load transfer during activities, which may result in an overload of stress on the ligaments of the pelvis.8,9
- Pressure on the spinal discs. While rare, about one in 10,000 (less than 1%) pregnant women may develop a herniated disc in the lumbar spine due to increased stresses on the disc(s) from the concurrent bodily changes.8,10 A herniated disc may in turn irritate, inflame, or mechanically compress a spinal nerve root in the lower back, causing sciatica symptoms to radiate into the thigh, leg, and/or foot.
- Transient osteoporosis. Weigh-bearing, especially in the third trimester, may cause some women to develop transient osteoporosis. This bone-weakening condition develops suddenly and causes hip pain and reduced range of motion in the hips.1
Previously existing lower back conditions, such as idiopathic scoliosis, rheumatoid arthritis, and ankylosing spondylitis, may worsen in pregnancy, increasing pain and other symptoms.8,9 Also, women who are younger, are of advanced maternal age, or have a history of lower back pain during menstruation may be at a higher risk of developing back pain in pregnancy.1,11
When to Seek Medical Attention
Back pain is often untreated and considered a normal and inevitable part of pregnancy among women. To help make pregnancy as pleasant as possible and to facilitate an easier delivery, back pain should be addressed and managed.
- Lower back pain that lasts a long time (several weeks or months) during pregnancy is usually a predictor for postpartum back pain. Pregnant women are encouraged to seek appropriate back pain treatment to prevent the recurrence of pain at later stages.
- Lower back pain that is associated with vaginal bleeding, lower right or left abdominal pain, groin pain, feeling faint, and tarry stools, may indicate a ruptured ectopic pregnancy, which is a medical emergency and must be treated on an urgent basis.12
- Postpartum pain that lasts longer than 6 to 8 weeks should be treated in order to avoid chronic back pain or recurring back problems after delivery. Over time, chronic pain can lead to psychological and psychosocial events that interfere with daily functioning and reduce the overall quality of life.
As a general rule, any concerning lower back symptoms must be discussed with a doctor without delay to ensure the safety of the mother and the growing fetus, as these symptoms may indicate ectopic pregnancy, preterm labor, or an infection.3
Cauda equina syndrome during pregnancy
Rarely, around 2% of pregnant women who have herniated lumbar discs may progress into a serious medical condition called cauda equina syndrome.13 In this syndrome, the herniation directly affects the cauda equina nerves that progress down from the spinal cord, disrupting nervous system signaling in the legs.
Typical symptoms of this condition include one or more of the following:
- Inability to pass urine, a reduced urinary sensation, a loss of desire to pass urine, or a poor stream
- Reduced or complete loss of bowel and/or bladder control
- Worsening neurological symptoms with intolerable pain
- Numbness in the groin, buttocks, and/or genital area (saddle anesthesia)
Cauda equina syndrome must be treated on an urgent basis to preserve leg function. Optimal management requires a multidisciplinary approach with several specialists, including the obstetrician, orthopedic specialist, neurologist, and/or neurosurgeon.
The many causes of lower back pain in pregnancy relate to biological, mechanical, postural, hormonal, and vascular factors. In most cases, several factors act together, resulting in pain. While pregnancy-related back pain typically subsides on its own, if the symptoms and signs worsen over time, consulting a doctor is advised.