One-Sided Pain in Early Pregnancy: What It Means

Feeling pain on one side of your lower abdomen in early pregnancy can be unsettling. In many cases it is a completely normal part of your body adjusting to the changes of early pregnancy. However, one-sided pain is also a classic warning sign of an ectopic pregnancy, so it always deserves attention rather than being dismissed. This guide helps you understand what is likely causing your pain and — crucially — when to act quickly.

Benign Causes of One-Sided Pain
When One-Sided Pain Is a Red Flag
How Doctors Assess One-Sided Pain
Managing Mild One-Sided Pain at Home
Frequently Asked Questions

Benign Causes of One-Sided Pain

Most one-sided pain in early pregnancy has a harmless explanation. Understanding the common causes can help you assess how worried to be.

Round ligament pain is one of the most frequent culprits. The round ligaments run from your uterus to your groin and, as your womb grows and shifts, they are put under increasing tension. This causes sharp, brief, stabbing pains — often on one side more than the other — particularly when you move suddenly, stand up quickly, cough, or sneeze. The pain typically lasts only seconds and fades completely with rest. It is very common from around six weeks onwards and is entirely harmless.

Corpus luteum cyst: After ovulation, the follicle that released the egg transforms into a structure called the corpus luteum, which produces progesterone to support the early pregnancy. Sometimes this forms a small cyst, which can cause aching or sharp pain on the side where you ovulated. These cysts almost always resolve on their own as the placenta takes over progesterone production around twelve weeks.

Implantation discomfort: Some women notice mild one-sided cramping or twinges around the time the embryo implants into the womb lining, typically around four to five weeks. This is normal and short-lived.

Constipation and bloating: Both are extremely common in early pregnancy due to the effects of progesterone on the digestive system. Trapped wind and constipation can cause localised cramping or pain that feels deceptively like gynaecological pain. If you have not opened your bowels recently and the pain is dull and shifting, this may be the cause.

Ovarian cysts unrelated to the corpus luteum: Some women have pre-existing ovarian cysts that are discovered incidentally during early pregnancy scans. Most are benign and monitored rather than treated, but they can occasionally cause pain if they twist (ovarian torsion), which is a separate emergency worth being aware of.

When One-Sided Pain Is a Red Flag

Certain combinations of symptoms mean you should seek help urgently rather than waiting to see if the pain passes.

Call 999 or go straight to A&E if you have:

Severe, persistent one-sided pain that is not easing
Pain with heavy bleeding (soaking a pad in under an hour)
Shoulder tip pain — an ache or sharp sensation at the very tip of the shoulder — which can indicate internal bleeding irritating the diaphragm
Dizziness, feeling faint, or actually fainting
A racing or pounding heart at rest
Sudden onset of extreme pain

These are the warning signs of an ectopic pregnancy — one where the embryo has implanted outside the uterus, most often in a fallopian tube. An ectopic pregnancy cannot continue and is not viable. If the fallopian tube ruptures, it causes internal bleeding that can be life-threatening. Ectopic pregnancies affect around one in every hundred pregnancies in the UK, and they are one of the leading causes of maternal death in the first trimester when not treated promptly.

Call your early pregnancy unit the same day if you have:

Persistent one-sided pain lasting more than a few hours, even if mild
One-sided pain with any amount of red bleeding, even light
One-sided pain with a positive pregnancy test but no confirmed intrauterine pregnancy yet on scan
Pain that is new, worsening, or different from the brief twinges you have noticed before

How Doctors Assess One-Sided Pain

When you attend your early pregnancy unit or A&E with one-sided pain, the team will typically:

Ask about the nature, location, and timing of your pain, and about any bleeding, dizziness, or shoulder tip pain
Take blood tests including hCG (pregnancy hormone) and sometimes progesterone levels
Perform an ultrasound scan — usually a transvaginal scan in early pregnancy, which provides much clearer images than an abdominal scan at this stage

If the scan shows a pregnancy clearly inside the uterus with a visible heartbeat, an ectopic pregnancy is effectively ruled out, and the team can investigate other causes of your pain. If the scan is inconclusive — which can happen very early in pregnancy — repeat blood tests 48 hours later help track how hCG is rising. A healthy intrauterine pregnancy will typically show a doubling of hCG over 48 hours; a slow rise or fall raises concern.

Managing Mild One-Sided Pain at Home

If you are confident the pain is round ligament pain or general pregnancy-related discomfort — brief, triggered by movement, settling quickly with rest — these steps may help:

Rest in a comfortable position; lying on the side that hurts is often soothing
Move more slowly and avoid sudden changes in position
A warm (not hot) water bottle applied to the area can ease ligament discomfort
Stay hydrated and ensure your bowels are regular, as constipation worsens pelvic pain
Paracetamol at the recommended dose is considered safe in pregnancy for pain relief; avoid ibuprofen in pregnancy unless specifically advised by your GP

If the pain is not easing, is worsening, or you feel at all unwell, stop managing at home and contact your midwife or EPU.

Frequently Asked Questions

Is mild one-sided pain normal at 6 weeks pregnant?

Yes, mild twinges on one or both sides are common at six weeks as your ligaments stretch, the corpus luteum cyst develops, and your uterus begins to grow. Brief, movement-related pains that ease with rest are usually benign. However, if the pain is severe, persistent, or accompanied by any bleeding or dizziness, you should contact your early pregnancy unit rather than waiting.

How do I know if it is round ligament pain?

Round ligament pain is typically sharp and brief — often described as a stabbing or pulling sensation — triggered by sudden movements such as standing up quickly, sneezing, or rolling over in bed. It usually lasts only a few seconds to a minute and resolves completely with rest. It tends to be worse on one side (often the right) and becomes more noticeable as the uterus grows. Pain that is severe, prolonged, or not related to movement is less likely to be round ligament pain and warrants assessment.

When should I go to A&E for one-sided pain in pregnancy?

Go to A&E immediately — or call 999 — if the pain is severe, if you have any bleeding alongside it, if you feel dizzy or faint, or if you have shoulder tip pain. These symptoms together point to a possible ectopic pregnancy, which is a medical emergency. If the pain is mild and you are unsure, calling your early pregnancy unit for advice is always a reasonable first step.

This information is for educational purposes only and does not replace professional medical advice. Always contact your midwife, GP, or early pregnancy unit if you are concerned about any symptoms in pregnancy. In an emergency, call 999.

Further reading:

NHS — Common pregnancy symptoms