An HSG, or hysterosalpingogram, is an X-ray test that checks whether your fallopian tubes are open and whether your uterus has a normal shape. It’s one of the first tests ordered during a fertility workup. A special dye is injected through your cervix, fills your uterus and fallopian tubes, and shows up on X-ray so a doctor can see the outline of these structures in real time.
How the Test Works
During an HSG, a thin catheter is inserted through your cervix into your uterus. A contrast dye flows through the catheter, filling your uterine cavity and then traveling into your fallopian tubes. As the dye moves, a series of X-ray images captures its path. If the dye flows freely through both tubes and spills out the ends, your tubes are open. If the dye stops at any point, it signals a blockage. Your body absorbs the dye on its own afterward.
The entire procedure typically takes only a few minutes. It’s done in a radiology suite or your doctor’s office, not an operating room, and you go home the same day.
What It Can Detect
The primary purpose of an HSG is to evaluate tubal patency, meaning whether your fallopian tubes are clear enough for an egg to travel through. But it reveals more than just blockages. The test can identify hydrosalpinx (a fluid-filled, swollen tube), adhesions around the tubes, and a condition called salpingitis isthmica nodosa where small outpouchings form in the tube wall.
Because the dye also fills the uterus, HSG can pick up uterine abnormalities: fibroids that push into the uterine cavity, polyps, scar tissue (synechiae) from prior surgeries or infections, and congenital shape variations like a septate or bicornuate uterus. It’s a relatively inexpensive, non-surgical way to get a broad picture of the reproductive anatomy. ACOG includes it as part of the standard basic infertility evaluation.
When It’s Scheduled
HSG is performed in the first half of your menstrual cycle, between days 1 and 14 (counting from the first day of your period). This timing serves two purposes: it reduces the chance you could be pregnant, and the uterine lining is thinner at this point, making the images easier to read. Your doctor’s office will coordinate the appointment based on your cycle.
What It Feels Like
Most women describe cramping in the lower abdomen that feels similar to period pain. The discomfort has two main sources: the catheter being placed through the cervix and the dye entering and expanding the uterus, which triggers uterine contractions. Some women feel a pressure or heaviness in the pelvis as the dye moves through.
For most people, the pain stays within a tolerable range and fades quickly once the procedure is over. If your tubes are blocked or you’re especially tense, the cramping can be more intense because the dye has nowhere to go and builds more pressure. In rare cases, women experience nausea, lightheadedness, or brief faintness. Doctors generally recommend taking an over-the-counter pain reliever about an hour before the procedure to take the edge off. You’ll typically rest for about an hour afterward before heading home, and any lingering discomfort usually resolves on its own.
Risks and Complications
HSG is considered a low-risk procedure. A large survey of over 5,000 women found that serious complications are uncommon. Pelvic inflammatory disease occurred in less than 0.5% of cases regardless of which type of dye was used. Allergic reactions to the contrast dye were extremely rare, reported in roughly 1 in 1,000 procedures, and no anaphylactic reactions occurred in the entire study population.
The most frequently reported complication was intravasation, where a small amount of dye enters the blood vessels near the uterus. This happened in about 1 to 5% of cases depending on the dye type and resolved without consequences. No cases of pulmonary embolism or death were reported. In some cases, doctors prescribe an antibiotic before the procedure as a precaution against infection.
One important note: tubal spasm can sometimes mimic a blockage on the images. The catheter or dye irritates the tube, causing it to clamp down temporarily. This can lead to a false positive result, where the test suggests a blockage that isn’t actually there. Your doctor may recommend repeat imaging or a different diagnostic approach if spasm is suspected.
The Unexpected Fertility Benefit
One of the more surprising findings about HSG is that the procedure itself may temporarily boost your chances of getting pregnant. A major randomized controlled trial from the Netherlands found that women who had an HSG with oil-based contrast dye had a pregnancy rate about 10% higher than those who received water-based dye in the six months following the test.
A more recent study focusing on women with endometriosis-related infertility found even more striking differences. The group that received oil-based contrast had a clinical pregnancy rate of 51% compared to 27% in the non-oil-based group, and live birth rates were also significantly higher (31% versus 20%). These benefits appeared across women who went on to try naturally, used intrauterine insemination, or pursued IVF. The exact mechanism isn’t fully understood, but one theory is that the oil-based dye physically flushes out minor debris or mucus plugs in the tubes, creating a clearer path.
Not every clinic uses oil-based contrast. The overall complication rate is somewhat higher with oil-based dye (5.1% versus 1.8% with water-based), mostly driven by the higher rate of intravasation rather than serious events. If this potential benefit matters to you, it’s worth asking which type of contrast your clinic uses.
Understanding Your Results
Results are usually available quickly, sometimes discussed with you right after the procedure. A normal HSG shows a smooth, triangular uterine cavity with dye spilling freely from both fallopian tubes. If one or both tubes appear blocked, it narrows the path forward: depending on where and how severe the blockage is, your doctor may recommend surgery, IVF (which bypasses the tubes entirely), or further testing with laparoscopy to get a direct visual look.
If the uterus shows an irregular shape, fibroids, polyps, or scar tissue, those findings help guide next steps too. Some uterine abnormalities can be corrected with a minor procedure, while others simply inform the overall fertility plan. HSG is a screening tool, not a definitive diagnosis for every condition it detects. Abnormal findings often lead to additional imaging or a surgical scope to confirm what the X-ray suggested.