Side pain during pregnancy is extremely common and usually caused by your body stretching to accommodate a growing uterus. The most frequent culprit is round ligament pain, which affects many pregnant people starting around week 14. But side pain can also come from digestive slowdowns, urinary issues, or, less commonly, conditions that need prompt medical attention. Understanding where the pain is, what it feels like, and when it started can help you figure out what’s going on.
Round Ligament Pain: The Most Common Cause
Two thick bands of tissue called the round ligaments run from the front of your uterus down into your groin. As your uterus grows rapidly during the second trimester (weeks 14 through 27), these ligaments stretch and pull, producing pain that can feel like aches, cramps, spasms, or a sharp stabbing sensation. It typically hits in the lower pelvis or groin area, and it can show up on one side or both.
What makes round ligament pain distinctive is how it behaves. It tends to flare with sudden movement: rolling over in bed, standing up quickly, coughing, sneezing, or laughing. The pain is usually brief, lasting seconds to minutes, and goes away on its own. It doesn’t come with bleeding, fever, or any other symptoms. If you can trace the pain back to a specific movement and it fades quickly, round ligament pain is the most likely explanation.
Slowing down your transitions helps. When you need to cough or sneeze, bending your knees and flexing your hips slightly takes tension off the ligaments. Changing positions gradually rather than popping up out of a chair reduces the sudden tug. Gentle prenatal stretching and warm (not hot) compresses can also ease the discomfort. Maternity support belts are widely marketed for this kind of pain, but research has found limited evidence that they actually reduce it, and some people report increased discomfort or skin irritation from wearing them.
Gas, Bloating, and Constipation
Pregnancy hormones do a number on your digestive system. Your body ramps up production of progesterone, which relaxes the muscles of your intestines so they don’t contract as forcefully. This slows everything down, giving your body more time to absorb nutrients and water from food. The trade-off is that stool dries out and becomes harder to pass, and food sitting longer in your gut produces more gas.
Trapped gas and constipation can create sharp, crampy pain that shifts around your abdomen, often settling on one side. The pain may come in waves and feel surprisingly intense. The key difference from other causes is that it tends to improve after a bowel movement or passing gas, and you’ll usually notice bloating, fullness, or irregular bowel habits alongside it. Staying hydrated, eating fiber-rich foods, and keeping physically active all help keep things moving.
Urinary Tract Infections and Kidney Stones
Pregnancy increases your risk of urinary tract infections, and when an infection travels up to the kidneys, it can cause a deep, dull ache in your side or flank (the area between your ribs and hip on your back). Kidney infections typically come with fever, chills, painful urination, or cloudy urine. This kind of pain doesn’t go away with position changes and tends to feel constant or worsening.
Kidney stones, while less common, also occur during pregnancy and produce intense, colicky flank pain that can radiate toward your groin. You might notice blood in your urine, pain that comes in strong waves, or an urgent need to urinate frequently. Both kidney infections and kidney stones need medical evaluation because they can trigger complications including preterm contractions.
Ectopic Pregnancy in the First Trimester
If you’re in early pregnancy (roughly the first 12 weeks) and feeling one-sided pelvic pain, ectopic pregnancy is an important possibility to rule out. This happens when a fertilized egg implants outside the uterus, most often in a fallopian tube. The first warning signs are typically light vaginal bleeding paired with pelvic pain on one side.
As the situation progresses, pain can become severe. If the tube ruptures, internal bleeding can cause shoulder pain (from blood irritating the diaphragm), extreme lightheadedness, or fainting. Any combination of sharp one-sided pelvic pain and vaginal bleeding in early pregnancy warrants immediate medical evaluation. An ultrasound can confirm whether the pregnancy is located inside the uterus.
Upper Right Side Pain: Preeclampsia and HELLP
Pain specifically in your upper right abdomen, under or near your ribs, carries a different set of concerns, particularly in the second half of pregnancy. This location corresponds to your liver, and liver-related pain is a hallmark of two serious conditions: preeclampsia and HELLP syndrome.
Preeclampsia involves high blood pressure (140/90 or higher) along with signs of organ stress, including protein in the urine, headaches, vision changes, or upper abdominal pain. HELLP syndrome is a severe variant that involves the breakdown of red blood cells, elevated liver enzymes, and low platelet counts. Upper right side pain is one of its signature symptoms, caused by swelling and stretching of the liver’s outer capsule.
These conditions develop after 20 weeks of pregnancy and can escalate quickly. Other warning signs include sudden swelling in the face or hands, a headache that doesn’t respond to rest or hydration, seeing spots or flashing lights, and nausea or vomiting that appears for the first time late in pregnancy. Blood pressure readings at or above 160/110 indicate severe disease. If you’re past 20 weeks and notice persistent pain under your right ribs alongside any of these symptoms, get evaluated right away.
Placental Abruption
Placental abruption occurs when the placenta separates from the uterine wall before delivery. The classic presentation is vaginal bleeding combined with abdominal pain, but it doesn’t always look textbook. In a concealed abruption, there’s little or no visible bleeding because the blood is trapped behind the placenta. In these cases, you might feel constant abdominal pain, and your belly may feel unusually firm or tender to the touch.
Abruption is most common in the third trimester and often accompanies abnormal contraction patterns. Risk factors include high blood pressure, trauma to the abdomen, smoking, and a history of previous abruption. Because abruption can compromise blood flow to the baby, sudden onset of constant abdominal pain (with or without bleeding) in later pregnancy needs urgent evaluation.
Preterm Labor Contractions
Before 37 weeks, regular contractions that produce a tightening or cramping sensation across your abdomen or sides could signal preterm labor. These contractions differ from the random, painless Braxton Hicks tightenings you might already be feeling. Preterm labor contractions tend to be regular, occurring every 2 to 3 minutes in active cases, and they may be accompanied by pelvic pressure, low back pain, or a change in vaginal discharge.
Clinical guidelines vary on exactly how many contractions per hour should prompt concern, with thresholds ranging from 4 to 12 per hour depending on the source. A practical rule: if you’re feeling four or more tightenings in an hour before 37 weeks, and they don’t stop when you rest, hydrate, and change positions, it’s worth calling your provider. Any contractions paired with bleeding, severe pain, or fluid leaking should prompt an immediate visit.
How to Sort Through Your Symptoms
Location, timing, and accompanying symptoms are the three things that help narrow down the cause of side pain in pregnancy. Pain low in the pelvis or groin that comes and goes with movement points toward round ligament stretching. Diffuse abdominal discomfort that improves after a bowel movement or passing gas is likely digestive. Deep flank pain with urinary symptoms suggests a kidney issue. Upper right pain after 20 weeks, particularly with headache or swelling, raises concern for preeclampsia or HELLP.
Pain that is constant, worsening, or accompanied by bleeding, fever, dizziness, or changes in the baby’s movement pattern falls outside the range of normal pregnancy discomfort. Trust what your body is telling you: brief, mild, and movement-related pain is almost always benign, while persistent or escalating pain deserves a call to your provider.