Pregnancy is an exciting journey, but it often comes with new aches and pains. One common complaint is left side back pain, which can range from a dull ache to sharp discomfort. In many cases, this pain is a typical result of pregnancy changes and is not harmful. However, it’s essential to know when left side back pain might signal something more serious. This blog provides expert-backed insights into the causes of left side back pain during pregnancy, tips for relief at home, and warning signs that indicate you should seek medical advice.
Common Causes of Left Side Back Pain During Pregnancy
Most back pain in pregnancy has a simple explanation. Understanding why it happens can put your mind at ease. Here are some common causes of left side back pain when you are expecting:
1. Hormone Changes (Relaxin)
During pregnancy, your body produces a hormone called relaxin that helps soften and loosen ligaments in preparation for childbirth. While this flexibility is necessary, it can strain the joints of your lower back and pelvis. You might feel this as an ache or instability, sometimes more on one side (often the left) if those joints are slightly imbalanced.
2. Posture and Weight Gain
As your baby grows, your centre of gravity shifts forward. This can lead you to adjust your posture, often unconsciously, for example, leaning back or to one side to balance the bump. Such changes put extra pressure on your back muscles. If you habitually favour one side, like carrying things on your left side or sleeping on one side, the muscles on that side can become fatigued and sore. Poor posture can also increase your risk of long-term spinal issues, as discussed in our guide on bad posture and chronic back pain.
3. Pelvic Girdle Pain (SPD)
Some pregnant women develop pelvic girdle pain, also known as symphysis pubis dysfunction (SPD). This condition involves pain in the pelvic joints and can radiate to the lower back or hip on one side. Relaxin and weight changes contribute to SPD, causing sharp or clicking pains in the back, hip, or groin. Pelvic girdle pain can be pretty uncomfortable, but the good news is that it does not harm your baby. It is a biomechanical issue affecting the mother’s joints. It tends to improve after delivery.
4. Round Ligament Pain
In the second trimester, you might experience a sudden, sharp pain in your lower belly or hip area when you change position. This is often round ligament pain. The round ligaments support your expanding uterus, and quick movements can make them tighten suddenly, causing a brief stabbing pain on either side. While round ligament pain is usually felt in the front or side of the abdomen, it can sometimes radiate around to the back or hip. It only lasts a few seconds and is considered a normal pregnancy pain that typically eases in later pregnancy.
5. Sciatica (Nerve Pressure)
The sciatic nerve runs from your lower spine down through your buttocks and legs. During pregnancy, your growing uterus, loosening ligaments, or a bulging disc can put pressure on this nerve, leading to sciatica. Sciatica causes a burning or shooting pain that may start in the lower back and travel down one leg, often only the left or right side. It can also cause numbness or tingling in the buttocks or legs. The pain might worsen as pregnancy progresses and your baby’s head or position adds pressure on the nerve. The comforting news is that while sciatica can be very painful for mum, it is not harmful to the baby and often goes away after the baby is born. In some cases, the pain may also be linked to facet joint syndrome, where irritation of the small joints in your spine contributes to nerve discomfort.
6. Uterine Growth and Postural Changes
Simply stretching to make room for your baby can cause twinges and aches. Many women notice general lower back soreness, sometimes more on one side, even early in pregnancy. This can be due to the uterus expanding and pulling on supporting structures. Later in pregnancy, the baby’s position might also contribute. For instance, if your baby tends to lie more to one side, you might feel more pressure and pain on that side of your back. These uterine changes are a regular part of pregnancy and often cause intermittent discomfort rather than constant pain.
Most of these causes are part and parcel of a healthy pregnancy. They tend to cause mild to moderate pain that comes and goes. However, not all back pain is harmless. It’s equally important to know the red flags.
When to Be Concerned: Warning Signs to Watch For
How do you know if left side back pain is just a normal pregnancy ache or something that needs medical attention? The general rule is to pay attention to other symptoms that accompany the pain and how severe or persistent the pain is.
- Fever, chills, or feeling unwell: Back pain with a fever could signal an infection, such as a kidney infection. A kidney infection can cause pain in your back or side along with symptoms like high temperature, shivering, or generally feeling sick.
- Pain when passing urine: If it hurts to pee, or your urine is cloudy or has blood in it, you may have a urinary tract infection that’s spreading toward the kidneys. UTIs are more common in pregnancy and can cause one-sided back/flank pain.
- Vaginal bleeding or fluid leakage: Any bleeding in pregnancy is a warning sign. If you have back pain on your left side along with spotting or bleeding, get medical advice right away. Similarly, if you feel a gush or trickle of fluid from your vagina with back pain, you should be evaluated.
- Regular contractions or tightening: Persistent low back pain that comes and goes in a pattern, or is accompanied by cramping in your lower belly, could mean you are having contractions.
- Second/Third Trimester Severe Pain: If you’re later in pregnancy and suddenly develop severe back pain on one side under your ribs, it could signal a more serious problem. For example, in rare cases, placental issues or preeclampsia can cause referred pain.
- Reduced baby movements: If your baby’s usual kicking and movement pattern has significantly decreased, and you also have back pain, treat that as urgent. While the two may or may not be related, decreased fetal movement is a vital sign that needs to be assessed immediately.
- Difficulty walking or numbness: If the pain is so bad that you struggle to walk, or you experience numbness/tingling in your legs or groin, seek medical help. Severe nerve compression can cause symptoms like leg weakness or loss of sensation.
Normal pregnancy back pain tends to be achy, positional, and relieved by rest or gentle movement. It shouldn’t be excruciating, and it usually isn’t accompanied by the alarming symptoms listed above.
The Role of Sleep and Recovery
Quality sleep plays a vital role in how your body heals and manages discomfort. Unfortunately, pregnancy can make it harder to rest, and sleep deprivation can worsen back pain. Using supportive pillows and maintaining good sleep posture can help reduce left side back pain and promote better rest.
Complementary Therapies
Some women find relief from therapies like prenatal massage or gentle stretching. For those open to alternative approaches, research suggests that acupuncture may help manage chronic back pain when performed by a trained practitioner experienced in pregnancy care. Always check with your healthcare provider before starting any new therapy.
When to Seek Medical Advice
If you are ever unsure about your pain, especially if it comes with other symptoms, reach out to your healthcare provider. They are there to help you. Inform them if you noticed any of the warning signs we listed earlier.
Doctors will usually ask a few questions and may do an exam or tests if needed. They might check your urine for infection or suggest an ultrasound if they suspect something like kidney stones or, in early pregnancy, to rule out an ectopic pregnancy. These tests are all to ensure you and your baby are healthy.
Remember, serious causes of left side back pain in pregnancy are not very common. Most mums-to-be with back pain do not have any significant complications. But being aware and getting timely advice will ensure that those that do occur are managed quickly.
Summary
Left side back pain is usually an everyday companion to pregnancy, caused by the incredible changes your body undergoes to support a growing baby. Factors such as hormonal ligament loosening, shifts in posture, and nerve pressure can all contribute to one-sided back aches. The reassuring news is that these pains are often manageable with simple lifestyle adjustments, supportive gear, and home remedies. By practising good posture, using pillows and heat, staying active with gentle exercises, and listening to your body’s signals, you can often find relief and continue your daily activities comfortably.
References
- NHS – Back pain in pregnancy: Explains common causes of backache in pregnancy and tips for avoiding pain, nhs.uk.
- Cleveland Clinic – Back Pain During Pregnancy: Overview of why back pain happens in pregnancy and safe relief strategies, my.clevelandclinic.org.
- MedicineNet – Is It Normal to Have Pain on Your Left Side During Pregnancy?: Covers causes of left side pain (including round ligament pain, PGP, and UTIs) and when to call a doctor, medicinenet.com.
- Bupa UK – Kidney infection (pyelonephritis): Lists symptoms of kidney infection such as one-sided back pain, fever, and urinary issues, bupa.co.uk.
- Cleveland Clinic (Health Essentials) – How to Handle Sciatica During Your Pregnancy: Provides insight into sciatic nerve pain in pregnancy and reassurance that it’s not harmful to the baby, health.clevelandclinic.org.
- NHS – When to get help for back pain in pregnancy: Advises contacting a GP or midwife urgently in cases of back pain with fever, vaginal bleeding, pain when peeing, or if in the second/third trimester due to potential early labour, nhs.uk.
