The shot given for ectopic pregnancy is methotrexate, a medication injected into the muscle (usually the buttock or thigh) that stops the pregnancy from growing so your body can reabsorb it over four to six weeks. It’s a well-established alternative to surgery for ectopic pregnancies caught early, with a success rate of about 91% in eligible patients.
How Methotrexate Works
Methotrexate is a folic acid antagonist, meaning it blocks your body’s ability to use folate, a vitamin that cells need to copy DNA and multiply. Without folate, the rapidly dividing cells of the pregnancy can’t replicate and eventually die. Your body then gradually breaks down and absorbs the tissue over several weeks. The drug targets fast-growing cells specifically, which is why it’s effective against early pregnancies while leaving the rest of your body largely unaffected at this dose.
Who Can Get the Shot
Methotrexate works best when the ectopic pregnancy is small and detected early. Your doctor will check your blood levels of hCG (the pregnancy hormone) to help predict whether the shot will work. Research suggests success rates are highest when hCG levels are relatively low. One study found that patients with hCG below roughly 1,350 mIU/mL were the best candidates, though doctors use a range of clinical factors to decide.
You won’t be offered methotrexate if you have liver or kidney problems, low blood counts (anemia or low white blood cells or platelets), signs of tubal rupture, hemodynamic instability, or if a fetal heartbeat is detected on ultrasound. Severe abdominal pain or an ectopic mass larger than 4 cm may also rule it out. In those situations, surgery is the safer option.
What the Treatment Looks Like
The most common approach is the single-dose protocol. You receive one intramuscular injection of methotrexate, dosed based on your body surface area (50 mg per square meter). Despite the name “single dose,” you may need additional injections depending on how your body responds.
After the shot, you’ll have blood drawn on day 4 and day 7 to track your hCG levels. Your doctor is looking for at least a 15% drop between those two draws. If your levels drop by that amount, you’ll continue with weekly blood tests until hCG reaches zero. If the drop is less than 15%, you’ll receive a second injection and the monitoring cycle starts again. If levels still aren’t falling after further doses, surgery becomes necessary.
There’s also a two-dose protocol, where you get a second shot on day 4 regardless, and a multi-dose protocol that involves injections every other day with a rescue medication given on alternating days to limit side effects. Your doctor will choose the protocol based on your hCG levels and clinical picture.
Common Side Effects
Most side effects are manageable and temporary. The most commonly reported ones include:
- Abdominal pain or cramping, which can be tricky because it may also signal tubal rupture
- Nausea, vomiting, or decreased appetite, typically within the first 24 hours
- Fatigue
- Mouth sores
- Diarrhea or upset stomach
- Redness or soreness at the injection site
- Headache or trouble sleeping
Some abdominal pain between days 3 and 7 is actually expected as the treatment takes effect. But if you experience sudden, sharp, or worsening pain, that could indicate a rupture, which is a medical emergency.
What to Avoid During Treatment
Because methotrexate works by blocking folate, you need to stop taking any supplements containing folic acid while the drug is active in your system. This includes most prenatal vitamins. Folic acid would counteract the medication and reduce its effectiveness.
You should also avoid heavy exercise and sexual intercourse until your treatment is complete and your doctor confirms your hCG has reached zero. The risk of the fallopian tube rupturing doesn’t disappear until the ectopic pregnancy is fully resolved, and physical strain or pressure in the pelvic area could increase that risk. Alcohol is also off-limits, since methotrexate is processed by the liver.
How Long Until You Can Try to Conceive Again
Methotrexate gets broken down into compounds that can linger in liver cells and reduce your folate stores for some time after treatment. The FDA recommends waiting at least one full ovulatory cycle after the drug clears your system before trying to conceive. Most doctors advise waiting three months to give your folate levels time to recover and to ensure any residual effects of the drug have passed. This waiting period helps reduce the risk of birth defects in a future pregnancy.
Research on women who received methotrexate for ectopic pregnancy has not shown lasting damage to fertility. Many go on to have healthy pregnancies afterward, though having had one ectopic pregnancy does increase your risk of having another, regardless of whether you were treated with the shot or surgery.