Ectopic pregnancy, where a fertilized egg implants outside the uterus (usually in a fallopian tube), affects roughly 1% to 2% of all pregnancies in the United States. While it can happen to anyone who becomes pregnant, certain factors significantly raise the odds. Ruptured ectopic pregnancies remain the leading cause of maternal death in the first trimester, so understanding your personal risk level matters.
Previous Ectopic Pregnancy
A prior ectopic pregnancy is one of the strongest predictors of having another one. The recurrence rate sits between 10% and 27%, depending on the study and the treatment used the first time around. That alone makes it the single most important risk factor to be aware of.
The risk compounds with each occurrence. Women who have had two previous ectopic pregnancies treated with surgical removal or repair of the fallopian tube face a roughly 10-fold increased risk of yet another ectopic compared to those who have had only one. If you’ve experienced an ectopic pregnancy before, your doctor will likely monitor any future pregnancy closely in its earliest weeks to confirm the embryo has implanted in the right place.
Pelvic Infections and STIs
Infections that reach the fallopian tubes are a major driver of ectopic pregnancy risk. Pelvic inflammatory disease (PID), often caused by untreated chlamydia or gonorrhea, creates scarring and inflammation inside the tubes. That scarring can physically block or slow a fertilized egg’s journey to the uterus, causing it to implant in the tube instead. Chlamydia-related inflammation of the fallopian tubes has been identified as a primary contributor to the rise in ectopic pregnancies over recent decades.
The damage doesn’t have to come from a dramatic infection. Even mild or “silent” chlamydia infections, the kind that cause no noticeable symptoms, can scar tubal tissue over time. This is one reason routine STI screening is valuable for sexually active women, particularly because the tubal damage is largely irreversible once it occurs.
Smoking
Smoking is one of the most well-established modifiable risk factors. Nicotine and its byproduct cotinine directly affect the fallopian tubes by altering the chemical environment inside them. In smokers, the tubes produce roughly two to three times the normal amount of a receptor protein involved in embryo implantation and blood vessel formation. This chemical shift can essentially trick the tube into becoming a hospitable site for the embryo to attach, rather than letting it pass through to the uterus.
Nicotine also impairs the smooth muscle contractions that help move the egg along the tube. Research shows that even passive smoke exposure produces enough cotinine in the blood to trigger measurable changes in fallopian tube tissue. The more you smoke, the higher the risk, but there is no safe threshold.
Age Over 35
Maternal age plays a significant role. Women aged 35 and older face a four- to eight-fold increased risk of ectopic pregnancy compared to younger women. The reasons are partly biological: older fallopian tubes may have reduced motility and accumulated subtle damage over years. Age also correlates with longer exposure to other risk factors like infections or endometriosis, making it difficult to separate age alone from the cumulative effect of time.
Tubal Surgery and Sterilization
Any surgery on or near the fallopian tubes raises ectopic risk. This includes tubal ligation (having your “tubes tied”), tubal ligation reversal, and surgeries to remove adhesions or repair blocked tubes. The procedures create scar tissue that can narrow the tube’s interior or disrupt the delicate lining that guides a fertilized egg toward the uterus.
Tubal ligation is highly effective at preventing pregnancy overall, but when it fails, the pregnancy that results is disproportionately likely to be ectopic. Data suggests that among pregnancies conceived after tubal ligation, roughly 15% to 20% are ectopic. That doesn’t mean sterilization causes ectopic pregnancies frequently in absolute terms. It means that on the rare occasion the procedure fails, the altered anatomy favors an ectopic implantation.
IUD Use and Contraception
Intrauterine devices (IUDs) are highly effective contraceptives, and they actually reduce your overall chance of any pregnancy, including ectopic. However, there’s an important nuance: if you do become pregnant with an IUD in place, the pregnancy is roughly six times more likely to be ectopic than a pregnancy conceived without an IUD. This is because IUDs are better at preventing implantation in the uterus than in the fallopian tube, so the rare failures skew toward ectopic location.
This doesn’t mean IUDs are dangerous. Your absolute risk of ectopic pregnancy while using an IUD is lower than if you were using no contraception at all. But if you have an IUD and experience signs of pregnancy, such as a missed period, unusual bleeding, or pelvic pain, it’s worth getting evaluated quickly to rule out an ectopic implantation.
Fertility Treatments
Women using assisted reproductive technology face a somewhat elevated risk. Ectopic pregnancies account for about 2% to 5% of pregnancies achieved through fertility treatments, compared to 1% to 2% in the general population. A large 10-year study of over 27,000 treatment cycles found an ectopic rate of 1.8% of all pregnancies achieved, which the authors noted was comparable to natural conception rates, though other research has found higher figures.
Among women undergoing fresh embryo transfers, a history of pelvic adhesions had the greatest impact, increasing the odds of ectopic pregnancy roughly 2.5 times. Other contributing factors included the woman’s age, hormone levels, whether blastocyst-stage embryos were transferred, and whether the transfer procedure itself was technically difficult. These findings suggest the underlying fertility issues, rather than the IVF process alone, drive much of the increased risk.
Other Contributing Factors
Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, can distort pelvic anatomy and damage fallopian tubes. Pelvic adhesions from any cause, whether prior surgery, infection, or endometriosis, create physical barriers that interfere with normal egg transport.
Structural abnormalities of the fallopian tubes, whether present from birth or acquired over time, also contribute. Some women have unusually long or irregularly shaped tubes that make it harder for an embryo to reach the uterus within the narrow window before it’s ready to implant. A history of abdominal surgery, even procedures unrelated to the reproductive system like an appendectomy, can occasionally produce adhesions near the tubes that increase risk.
How Early Detection Works
If you have one or more risk factors, early monitoring in pregnancy can catch an ectopic before it becomes dangerous. One of the key tools is tracking the pregnancy hormone hCG through blood draws taken 48 hours apart. In a normal early pregnancy, hCG levels roughly double every two days or faster. In most ectopic pregnancies, hCG rises more slowly, with a doubling time exceeding 2.2 days, or it may plateau or decline. When hCG patterns are sluggish, transvaginal ultrasound is used to look for a gestational sac inside the uterus. If no intrauterine pregnancy is visible at the expected hCG level, an ectopic diagnosis becomes likely.
Knowing your risk factors doesn’t guarantee an ectopic will happen, but it gives you and your care team a reason to watch more carefully in those first weeks. The earlier an ectopic pregnancy is identified, the more treatment options are available and the lower the chance of a life-threatening rupture.