A minority of pregnant women, and no UK figuresEmerging evidence
In one Turkish hospital study of 184 women, 6.0% reported shoulder pain in the first trimester, 7.6% in the second and 8.2% in the third, with no clear rise late in pregnancy; about a third reported carpal tunnel symptoms. No study has made shoulder pain in pregnancy its main question, and there is no UK figure. In a survey of 1,651 Israeli women, back pain differences between pregnant and non-pregnant women disappeared once general health and other factors were allowed for (the shoulder wasn't reported in the summary we read).
The UK's pelvic and obstetric physiotherapists (POGP) say muscle and joint symptoms are most likely in the third trimester, can start earlier or carry on after the birth, and "In most cases symptoms will improve after you give birth".
Sources 1, 2, 3
Commoner after the birth, with feeding and carryingEmerging evidence
In 216 breastfeeding mothers at a Turkish clinic, 34.3% had shoulder pain, more with the cross-cradle hold; rocking the baby to sleep in the arms went with more arm and shoulder disability, and help at home with less. In an online survey of 471 mothers, about 3 in 10 named the shoulder, arm or hand as the painful area. In 308 Japanese women a month after the birth, most neck and shoulder pain was across the top of the shoulder, linked with time spent on each feed and tiredness, and in 2,413 Swedish women, neck and shoulder pain was common at 2 months and a year after the birth.
These are surveys, mostly outside the UK, which can't show cause.
Sources 4, 5, 6, 7
Why it happens: the neck, posture, joints and carryingEmerging evidence
"Occasionally, problems felt in your shoulder can be due to a neck problem. This can happen even when you don't feel pain in your neck", NHS inform says. POGP lists posture changes as the baby grows, more flexible joints, enlarged breasts, feeding in an awkward position and lifting and carrying after the birth.
The evidence for each is thin. Spinal curves change in pregnancy, but not consistently, and back pain didn't track the changes in a review of 50 papers; in adults who aren't pregnant, a rounded upper back wasn't linked with shoulder pain. No study has looked at shoulder looseness in pregnancy: wrist looseness rose in 19 of 35 pregnant women but didn't track relaxin, and the one study linking relaxin to shoulder instability was in young athletes who weren't pregnant. Front or back baby carriers load the wearer's body less than carrying a baby in your arms.
Sources 8, 3, 9, 10, 11, 12, 13
The rotator cuff and frozen shoulderStrong evidence
Rotator cuff (subacromial) pain is "the most common reason for shoulder pain", NHS inform says: pain in the upper arm when you lift it above shoulder level or reach behind your back, and it may be hard to lie on that side. The arm moves fully when someone else lifts it, which is how a clinician tells it from a frozen shoulder.
A frozen shoulder causes pain near the top of the arm and a large loss of turning the arm out. It typically affects women between 45 and 60, and diabetes is the strongest link (10.8% with diabetes against 2.3% without, in the British Elbow and Shoulder Society's pathway). No study links frozen shoulder or rotator cuff pain with pregnancy or gestational diabetes, so in pregnancy a frozen shoulder is likely to be uncommon.
Sources 14, 15, 16, 17, 18, 19
Causes that aren't the shoulder, and how rare they areStrong evidence
"Shoulder tip pain is an unusual pain felt where your shoulder ends and your arm begins", and it can be a sign of an ectopic pregnancy causing some internal bleeding, the NHS says. About 1 in 90 UK pregnancies is ectopic, with symptoms usually between the 4th and 12th week; ruptures are uncommon and treatable, and deaths from them are extremely rare in the UK.
Later in pregnancy, pain under the ribs that is "bad or persistent, particularly on the right side, ... can be a sign of pre-eclampsia", which usually starts after 20 weeks or just after the birth, the NHS says. HELLP syndrome, a rare liver and blood disorder linked with it, affects 0.5% to 0.9% of pregnancies, and acute fatty liver of pregnancy about 5 in 100,000. Gallstone pain sits under the right ribs and "may spread from here to your side or shoulder blade" (NHS inform); new gallbladder sludge or stones showed on scans in about 1 in 20 women by mid-pregnancy, and most gallstones cause no symptoms.
Clots affect only 1 to 2 in 1,000 women in pregnancy or the 6 weeks after, the Royal College of Obstetricians and Gynaecologists (RCOG) says. A heart attack in pregnancy or the week after is rarer still: 0.7 per 100,000 maternities in the UK.
Sources 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32
Where to get help, and how fastStrong evidence
Pelvic pain with pain in the tip of your shoulder, or bleeding in pregnancy with shoulder pain, is a 999 call, the NHS says. An inflamed gallbladder causes a sudden, sharp pain under the right ribs that "spreads towards your right shoulder". Heart pain can spread to either arm, the neck, jaw or shoulder, and sudden breathlessness with chest or upper back pain is a 999 call. A hot, swollen joint with a high temperature needs help the same day.
Otherwise, where to turn in pregnancy depends on how far along you are: your GP surgery or early pregnancy unit in the first 12 weeks, your midwife or early pregnancy unit from 12 to 19 weeks, and your midwife or maternity unit from 20 weeks. Call NHS 111 if you're not sure what to do.
Sources 33, 34, 35, 36, 37, 38, 39, 40
Shoulder tip pain after a caesarean is commonEmerging evidence
In 165 women having a planned caesarean under a spinal anaesthetic, 49.6% had shoulder tip pain during or after it, and a review says it usually settles within about 72 hours. Heavy bleeding, feeling faint or breathlessness are the warning signs, not the shoulder pain itself.
Sources 41, 42
When a scan or test helpsStrong evidence
Rotator cuff pain and frozen shoulder are diagnosed from the story and an examination, not a scan. An X-ray is for a fall or a suspected break or dislocation: tell the radiographer you're pregnant, and UK guidance says the dose to the baby from diagnostic X-rays "should present no risk", with ultrasound or MRI considered first where they would answer the question.
A suspected ectopic pregnancy needs a pregnancy test, then an ultrasound scan and blood tests; gallstones are found with an ultrasound scan and a blood test; and nerve tests for carpal tunnel "are not essential to make a diagnosis".
Sources 14, 17, 43, 44, 45, 21, 27, 46
How it usually goesEmerging evidence
Most muscle and joint symptoms of pregnancy improve after the birth (POGP). Rotator cuff pain "usually gets better in a few weeks or months", though "It can take 6 months or longer to recover from shoulder pain", the NHS says, and a frozen shoulder can take more than 2 years. Carpal tunnel often eases after the birth but can last a year or more. No one can promise a timescale.
Sources 3, 15, 47, 18, 48, 49