A failed abortion means an attempt to end a pregnancy that did not fully work. The term covers two distinct situations: an ongoing pregnancy where the fetus continues to develop despite the procedure or medication, and an incomplete abortion where the pregnancy has ended but tissue remains inside the uterus. Both require follow-up care, but they carry different risks and involve different next steps.
Ongoing Pregnancy vs. Incomplete Abortion
These two outcomes are often lumped together under “failed abortion,” but they’re medically quite different. An ongoing pregnancy means the embryo or fetus survived the procedure and continues to grow. This is relatively rare, occurring in roughly 0.5% of medical abortions that use the standard two-drug regimen. An incomplete abortion means the pregnancy itself has ended, but some tissue hasn’t been expelled from the uterus. The cervix may still be partially open, and bleeding often continues. Both situations need medical attention, but the urgency and treatment options differ.
How Often Abortions Fail
Medical abortion using the standard two-drug combination is effective about 98% of the time overall, but success rates shift with gestational age. At four weeks, the failure rate is less than 1%. By week eight (around 56 to 59 days), it rises to about 4.3%. When the second medication is taken orally rather than placed inside the cheek, failure rates are somewhat higher, reaching about 7% at seven weeks.
Surgical abortion by aspiration (vacuum suction) succeeds roughly 98% of the time. About 2% of patients need a repeat procedure or additional intervention. Failure can happen when the uterus has an unusual shape, when the pregnancy is very early and the tiny sac is missed, or in rare cases when the instruments don’t reach the correct location.
Signs That an Abortion May Not Have Worked
The most common symptom after an unsuccessful or incomplete abortion is heavy or prolonged vaginal bleeding, reported by about 78% of patients who experienced complications in one study of self-administered medical abortion pills. Other warning signs include:
- Persistent pregnancy symptoms like nausea, breast tenderness, or fatigue that don’t fade within a week or two
- Abdominal or pelvic pain that continues or worsens rather than gradually improving
- Irregular bleeding that starts and stops without a clear pattern
- No passage of tissue after taking abortion medication, reported in about 7% of complicated cases
A follow-up visit, typically scheduled one to two weeks after the procedure, is when most failures are caught. Ultrasound can confirm whether the uterus is empty, whether tissue remains, or whether a pregnancy is still viable. In some protocols, blood hormone levels are tracked to confirm they’re dropping as expected.
What Happens If Tissue Is Left Behind
When pregnancy tissue stays in the uterus, the body treats it as something that needs to come out. This causes continued bleeding and cramping. If it isn’t addressed, the retained tissue can become a source of infection, leading to fever, foul-smelling discharge, and worsening pelvic pain. In severe cases, untreated infection can progress to sepsis.
There are also longer-term risks. Retained tissue can trigger the formation of scar tissue inside the uterus, a condition called Asherman syndrome. These adhesions can cause menstrual irregularities, make future pregnancies more difficult, and increase the risk of complications like ectopic pregnancy or abnormal placenta attachment. In rare cases, leftover tissue develops an abnormal blood supply, which can cause sudden, severe hemorrhage weeks or even months later.
Treatment for retained tissue usually involves either a second dose of medication to help the uterus contract and expel the remaining tissue, or a brief aspiration procedure to remove it directly. In one large trial published in the New England Journal of Medicine, 71% of women treated with medication had complete expulsion after a single dose, and 84% after a second dose given a few days later. Those who still had retained tissue after both doses then had a surgical aspiration.
Risks of a Continuing Pregnancy After Medication Exposure
When an ongoing pregnancy is discovered after a failed medical abortion, a key concern is whether the medications may have affected fetal development. The second drug in the standard regimen causes strong uterine contractions, and these contractions can reduce blood flow to the developing embryo. This mechanism has been linked to a range of rare but serious birth defects.
Reported abnormalities include limb development problems such as clubfoot, fused fingers, and in rare cases, absence of a limb bone. The contractions can also damage developing cranial nerves, leading to Moebius syndrome, a condition that affects facial movement and the ability to move the eyes side to side. Jaw abnormalities and, in isolated cases, fluid buildup in the brain have also been documented. These outcomes are rare, but they are the reason clinicians strongly recommend confirming that a medical abortion was successful rather than assuming it worked.
How a Failed Abortion Is Managed
If the pregnancy is still ongoing, the options depend on gestational age and the patient’s wishes. A surgical aspiration can be performed, or in some cases a second course of medication may be offered. The further along the pregnancy, the more likely a surgical approach will be recommended.
If the issue is retained tissue rather than an ongoing pregnancy, the choice is typically between watchful waiting with a follow-up ultrasound, a repeat dose of medication to encourage the uterus to empty, or an aspiration procedure. Aspiration is a brief outpatient procedure that takes only a few minutes and resolves the issue in the vast majority of cases. In the New England Journal of Medicine trial, surgical management had a failure rate of only 3% by 30 days, compared to 16% for medication management of incomplete abortion.
Most patients are contacted by phone about a week after treatment to check on symptoms, then return for an in-person follow-up around two weeks. By that point, ultrasound or a physical exam can confirm whether the uterus has fully emptied and healing is on track.