Back Pain in Pregnancy

What is actually happening

The NHS gives the mechanical explanation: "During pregnancy, the ligaments in your body naturally become softer and stretch to prepare you for labour. This can put a strain on the joints of your lower back and pelvis, which can cause back pain."

ACOG fills in the rest of the picture. Your expanding uterus "shifts your center of gravity and stretches out and weakens your abdominal muscles", which changes your posture and puts strain on your back — and because your abdominal muscles normally help support your spine, weakening them removes part of the support system. The extra weight means more work for your muscles and more stress on your joints, "which is why your back may feel worse at the end of the day". On hormones it is direct: a hormone relaxes the ligaments in your pelvic joints, and "back pain can occur if the joints become too flexible".

The HSE adds the ordinary aggravators: tiredness and stress make it worse.

How common? Cochrane's reviewers say "more than two-thirds of pregnant women experience low-back pain and almost one-fifth experience pelvic pain", and note that both typically increase as pregnancy advances, "interfering with work, daily activities and sleep". ACOG calls backache "one of the most common pregnancy problems, especially in the later months".

What is normal

An ache low in the back that builds through the day, is worse after standing, lifting or a long commute, and eases with position changes and rest. It usually starts in the second half of pregnancy and gets more insistent as the bump grows.

Recovery is usually good but not instant. ACOG: "The pain usually goes away after the baby is born. But for many women, back pain lingers for months after giving birth."

Worth distinguishing: pain that sits over the pubic bone, the back of the pelvis or between the legs, or that gets sharply worse turning over in bed or climbing stairs, is more likely pelvic girdle pain — a related but separate problem with its own management. NICE recommends considering referral to physiotherapy for exercise advice and a non-rigid lumbopelvic belt for pregnancy-related pelvic girdle pain.

What is not normal

Back pain is one of those symptoms that occasionally belongs to something else entirely, and the list of things it can be is short and specific.

The NHS says to contact your GP or midwife urgently if:

• You have back pain in the second or third trimester — this can be a sign of early labour.
• Your back pain comes with a fever, vaginal bleeding, or pain when you pee.
• You have pain in your sides, under the ribs.

ACOG's version overlaps almost exactly: back pain can be a symptom of preterm labour, and can be a sign of a urinary tract infection — so contact your maternity care provider if you also have a fever, burning on urination, or vaginal bleeding. It adds a duration rule: call if the pain is severe, or if it goes on for more than two weeks.

Call your local emergency number (999 in the UK and Ireland, 911 in the US and Canada, 000 in Australia, or 111 in New Zealand) or go to an emergency department if you have "loss of feeling in one or both of your legs, your bum, or your genitals" (NHS). The HSE adds loss of bowel or bladder control to the same emergency list. This combination can indicate pressure on the nerves at the base of the spine and is time-critical.

What actually helps

Exercise — the one with real evidence

The Cochrane review of interventions for low-back and pelvic pain in pregnancy included 34 randomised trials involving 5121 women, and it is the best evidence available. The headline findings:

• Land-based exercise significantly reduced low-back pain (standardised mean difference -0.64, 95% CI -1.03 to -0.25; 645 women, seven studies) and functional disability — low-quality evidence.
• An eight- to 12-week exercise programme reduced the number of women reporting combined low-back and pelvic pain (RR 0.66, 95% CI 0.45 to 0.97; 1176 women, four studies) — moderate-quality evidence.
• Land-based exercise significantly reduced pain-related sick leave (RR 0.76, 95% CI 0.62 to 0.94) — moderate-quality evidence.

There was also moderate-quality evidence from individual studies that osteomanipulative therapy reduced low-back pain and disability, and that acupuncture or craniosacral therapy improved pelvic pain more than usual care.

The reviewers' own caution matters: the quality of evidence "ranged from moderate to low, raising concerns about the confidence we could put in the estimates of effect". So: exercise is the best-supported option, and "best-supported" here means a moderate-quality signal rather than a certainty.

In practice that means a structured programme over a couple of months rather than a stretch when it twinges. ACOG notes water exercise is especially useful because "the water supports your weight so you avoid injury and muscle strain", and that walking is safe and good for the back. Tommy's suggests pilates, yoga or swimming, and staying active rather than resting up.

The everyday mechanics

The NHS list is worth following properly: bend your knees and keep your back straight when lifting; avoid lifting heavy objects; move your feet to turn rather than twisting your spine; balance shopping between two bags; sit with your back supported, using a cushion; get enough rest, especially later on; and try a massage, a warm bath or a firm mattress. It suggests paracetamol for pain relief unless your midwife or doctor has advised otherwise.

There is one useful disagreement between sources, and it is worth naming rather than smoothing over. The NHS advises wearing flat shoes to distribute your weight evenly. ACOG advises "low-heeled (but not flat) shoes with good arch support", on the grounds that completely flat shoes offer no support. Both agree on avoiding high heels. Either is defensible; comfort and arch support are what you are actually after.

ACOG also suggests an abdominal support garment to take the weight of your bump off your back muscles, a pillow between your knees when sleeping on your side, and heat or cold — wrapped in a towel, with the heating pad on its lowest setting.

An exercise you can do today

The NHS describes a simple one: on hands and knees with knees under hips, hands under shoulders and a flat back, pull in your stomach muscles and gently raise your back towards the ceiling, letting your head relax forward. Hold for a few seconds, then slowly return to a flat back. Repeat 10 times, moving slowly and rhythmically, and only as far as is comfortable.

Getting referred

Both the HSE and Tommy's point in the same direction if self-help is not enough: talk to your GP or midwife, who may refer you to a physiotherapist — Tommy's specifies an obstetric physiotherapist, who can give tailored advice. Tommy's also notes that acupuncture has research support, while cautioning that the practitioner should be qualified and told you are pregnant, because some points are not used in pregnancy.

The short version

Back pain in pregnancy is extremely common, mechanical, and usually improves after birth. Exercise over eight to 12 weeks is the intervention with the best trial support; posture, lifting technique and paracetamol fill in around it. The pain that needs a call today is rhythmic pain, pain with fever, bleeding or burning on peeing — and any numbness in your legs or genitals is an emergency.