HSG Test (Hysterosalpingography): What It Is, What to Expect, and Folic Acid

An HSG test (hysterosalpingography) is an X-ray procedure that shows the inside of the uterus and fallopian tubes, most often to see whether the tubes are partly or fully blocked.¹ It can also show whether the inside of the uterus is a normal size and shape.¹ This page explains why HSG is used in a fertility workup, how it is done according to ACOG, what to expect afterward, alternatives, and why folic acid belongs in the plan for anyone trying to conceive.

What is an HSG test?

During HSG, a contrast agent (a fluid containing dye) is placed in the uterus and fallopian tubes. The dye shows up on an X-ray screen, outlining the inner size and shape of the uterus and tubes and showing how the fluid moves through them.¹ If the tubes are open, the fluid spills slowly out of their far ends and is absorbed by the body.¹

The fallopian tubes are the passages an egg travels through from the ovary to the uterus.² Scarring or blockage of the tubes, from past sexually transmitted infections or endometriosis, is one of the health problems that can affect fertility.² HSG looks for that kind of scarring and for abnormalities in the uterus that can lead to infertility and pregnancy problems.¹

Why HSG is part of a fertility workup

An infertility evaluation includes exams and tests to try to find why a couple has not become pregnant. If a cause is found, treatment may be possible, and in many cases infertility can be treated successfully even when no cause is found.²

ACOG notes that experts recommend an evaluation at these points:²

Basic testing for women may include blood tests (progesterone to check ovulation, thyroid function, prolactin, and ovarian reserve), a urine test to detect ovulation, and imaging tests and procedures.² HSG is one of those imaging options, alongside ultrasound, sonohysterography, hysteroscopy, and laparoscopy.² Not everyone has every test, and some are chosen based on earlier results.² Testing for men often starts with a semen analysis.²

If you are tracking ovulation at home while you wait for an evaluation, our guide to the best ovulation tests explains how urine LH tests work.

When HSG is not done

ACOG lists these reasons HSG is not done:¹

• You are pregnant (you may be asked to take a urine pregnancy test before the procedure)
• You have a pelvic infection
• You have uterine bleeding at the time of the procedure
• You have a moderate to severe allergy to contrast dye

HSG is best done in the first half of the menstrual cycle (days 1 to 14), which reduces the chance that you could be pregnant.¹ Our page on the pregnancy blood test explains how hCG tests detect pregnancy.

How to prepare for an HSG

Talk with your ob-gyn about pain relief when you first discuss the procedure.¹ Options may include an over-the-counter pain reliever taken about an hour beforehand, or local anesthesia (a cream, gel, or injection that numbs the cervix) given right before the procedure.¹ In some cases you may be given an antibiotic to take before and after HSG.¹

HSG is done in a hospital, clinic, or ob-gyn office.¹ Most people can drive themselves home, but you may not feel well afterward, so consider arranging a ride.¹

What happens during the procedure

ACOG describes the steps this way:¹

1. You lie on your back with your feet positioned as for a pelvic exam. A speculum is placed in the vagina so the cervix can be seen, and the cervix is cleaned.
2. Local anesthesia may be applied to the cervix.
3. The dye is introduced in one of two ways: a cannula inserted into the cervix, or a thin plastic tube with a small balloon at the end that is inflated to hold it in place in the uterus.
4. The speculum is removed and you are positioned under the X-ray machine. The fluid is placed slowly into the uterus and tubes, which may cause cramping. If the tubes are blocked, the fluid causes them to stretch.
5. X-ray images are taken as the fluid fills the uterus and tubes, and you may be asked to change position.
6. The speculum and cannula or tube are removed after the images are taken.

After the procedure: what is normal and what is not

Afterward you can expect sticky vaginal discharge as some fluid drains out, and it may be tinged with blood. Use a pad rather than a tampon.¹ You may also have slight vaginal bleeding, cramps, or feel dizzy, faint, or sick to your stomach.¹

Severe problems after HSG are rare. They include an allergic reaction to the dye, injury to the uterus, or pelvic infection.¹

Alternatives to HSG

Other procedures can provide some of the same information, but not all of them show the fallopian tubes.¹

Your ob-gyn or a reproductive endocrinologist (an ob-gyn with special training in infertility) will recommend which tests fit your situation.²

Folic acid while you are trying to conceive

If you are having an HSG as part of a fertility workup, it is a good moment to check your folic acid. USPSTF recommends that everyone planning or capable of pregnancy take a daily supplement containing 400 to 800 mcg of folic acid, starting at least one month before conception and continuing through the first two to three months of pregnancy.³⁴ CDC recommends 400 mcg of folic acid every day for everyone who could become pregnant.⁵

Timing is the reason. The neural tube normally closes about 26 to 28 days after fertilization, often before a pregnancy is recognized.⁴⁶ Folic acid is the only form of folate shown in studies to help prevent neural tube defects, so look for "folic acid" on the Supplement Facts panel.⁷⁵ More is not better for average-risk people, and fertility claims for extra folic acid in people with adequate folate are unproven.⁸⁹

Some situations call for preconception counseling rather than a standard dose, including a previous pregnancy affected by a neural tube defect, a personal, partner, or family history of NTDs, certain antiseizure medicines, malabsorption after bariatric surgery, pregestational diabetes, and obesity.¹⁰³ For details, see folic acid before pregnancy and how much folic acid to take for pregnancy. If you are weighing other products, our guide to fertility supplements for women explains what the evidence does and does not support.

When to talk to a clinician

Bring a list of your medicines and supplements, including any prenatal vitamin, to your fertility appointment.²¹¹

This article is for general education and is not medical advice. Doses and needs differ from person to person, so talk with your clinician or pharmacist about your situation. Read our editorial policy and medical disclaimer.