Updated: Nov 26, 2020
As many as 80% of pregnant women will experience low back pain, especially in the their third trimester of the pregnancy. 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.
Typically, the pain will be in the sacroiliac joints, and is probably due to a combination of carrying extra weight and hormonal factors that act to widen the sacroiliac joints and increase the size of the birth canal.
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.
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.
While in most cases back pain is self-limiting, resolves after delivery, and does not cause lasting issues, some women may continue to be affected by pain in the lumbar and/or pelvic region for several months or years. In general, women who receive postural and activity-related counseling during pregnancy are less likely to develop severe back pain symptoms.
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. Pregnancy-related symptoms and signs affecting the lower back typically result in reduced overall function and include (but are not limited to):
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).
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.
Common Causes of Back Pain in Pregnancy
The cause of back pain in pregnancy is often considered multifactorial, meaning several factors act concomitantly on various structures in the lower body, causing pain. These factors are commonly recognized as the anatomical, postural, vascular, and hormonal changes that take place naturally during the course of pregnancy.
While most of these changes are considered normal, rarely, a few causes of lower back pain in pregnancy may indicate serious conditions, some of which may even be life-threatening.
Musculoskeletal Causes of Pregnancy Back Pain
During pregnancy, new changes in the mechanics of the lower back may occur, and many existing conditions may become worse, adding to the discomfort.
New changes in posture and stability of the lower back
The instability of the pelvis and lower back occurs due to the increase in the size of the uterus. These changes cause the spine to alter its shape, making the lower back more curved than usual. Muscles that stabilize the pelvis, such as the psoas, are shortened, further increasing the curvature of the lower back and causing pain.
Laxity of soft tissues and joints
The concentration of the relaxin hormone rises considerably during pregnancy, which increases tissue and joint flexibility in the lower back. The sacroiliac joints may become increasingly lax under the influence of this hormone. Since the sacroiliac joints are responsible for maintaining pelvic stability and transferring loads from the spine to the legs, the loosening of these joints may add to postural problems and increase the risk of back pain.
Widening of the pelvis
The concentration of the estrogen hormone also increases during pregnancy. The combined effects of relaxin and estrogen cause the pelvis to widen. This widening begins during the 10th to 12th week of pregnancy and causes the pelvis to increase in width by 10 mm or less. Pelvic pain typically becomes more in the later stages of pregnancy and may rapidly progress, causing severe pain in the lower back and thighs. The muscles and soft tissues in the area are often affected, causing pain while walking and resulting in an altered gait.
Neural Causes of Pain During Pregnancy
The peripheral nerves, such as the lateral femoral cutaneous nerve, in the pelvis and thigh region may become compressed, stretched, or lose blood supply, making them the primary source of pain. Swelling of the soft tissue may cause additional mechanical pressure on these nerves, causing thigh pain and referred pain in the lower back and pelvis.
Concomitant medical conditions, such as obesity, diabetes, and anatomical variations increase the risk of peripheral nerve pain in the legs.
Herniated Disc Pain in Pregnancy
Rarely, the increased stress and strain on the lower skeletal system and musculature may affect the spinal discs, resulting in herniation. A herniated lumbar disc may affect the nearby nerve roots causing sciatica symptoms to travel down the thigh and leg, and possibly into the foot. The medical term for sciatica is radiculopathy and typically affects one side of the body.
Weakening of the Hip Bone and Joint
Rarely, some women may develop a bone-weakening condition called osteoporosis in the third trimester of pregnancy.. The symptoms may appear slowly or suddenly, affecting the tissues of the hip joint, causing pain and limited hip motion.
Another condition that affects the hip region, avascular necrosis of the femoral head, may occur due to biological changes in pregnancy. These changes typically include weight gain and production of high levels of natural steroids, which may cause destruction of bone tissue in the femoral head (top part of the thigh bone), resulting in groin and lower back pain.
Placental Location and Back Pain
A posterior (back) location of the placenta (the tissue that provides nourishment to the fetus) is known to cause back pain in some pregnant women. In these cases, the placenta is located near the posterior wall of the uterus.
Ruptured Ectopic Pregnancy
Severe lower back and groin pain may occur when the fallopian tube ruptures due to an ectopic pregnancy. This condition is a medical emergency and occurs in early pregnancy, typically within the first few weeks or first trimester.
Infection and Back Pain
Urinary tract infections and kidney infection (pyelonephritis) may cause lower back pain. The pain is typically characterized as a dull and persistent ache accompanied by fever and/or chills. These conditions may carry a risk of preterm labor in some women.
Obstetrical Conditions that May Cause Back Pain
While not common, certain obstetrical conditions, such as spontaneous abortion, ovarian cysts, pelvic or uterine adhesions, fibroids, or collection of fluid, may cause lower back pain in pregnancy.
Back pain may also result as a sign of labor (full-term or pre-term) and is typically associated with uterine contractions that gradually increase in intensity.
Daily Activities that May Cause Back Pain
In addition to the conditions listed above, a few other factors can cause pain in the lower back or posterior pelvis. These factors typically include activities that create asymmetrical loading of the spine, pelvis, and hips. Common activities that load the spine in an uneven form include:
Walking and/or running
Rolling over in bed
Twisting the spine
Lifting objects off the floor
Back pain is common in pregnancy and typically resolves after delivery, but several conditions causing this symptom require medical attention to prevent future complications. Seeking medical care for pregnancy-related back pain is advisable. A physician can accurately diagnose the cause of back pain and provide the needed care for treating the symptoms.
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.
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.
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. 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)