An intrauterine device (IUD) is a small, T-shaped form of long-acting, reversible contraception placed inside the uterus to prevent pregnancy. An ectopic pregnancy occurs when a fertilized egg implants and begins to grow outside of the main uterine cavity, most commonly within a fallopian tube. While IUDs are highly effective birth control, significantly reducing the overall chance of pregnancy, a pregnancy that does occur with an IUD in place carries a higher relative chance of being ectopic.
Risk Levels and Mechanism
Understanding the difference between absolute risk and relative risk is key. The absolute risk—the overall chance of having an ectopic pregnancy while using an IUD—is very low, much lower than for those using no contraception. This is because IUDs, both hormonal and copper, are highly effective, resulting in a pregnancy rate of less than 1% per year.
The relative risk refers to the likelihood of an ectopic pregnancy if the IUD fails and a pregnancy occurs. IUD mechanisms primarily prevent implantation within the uterus. The copper IUD prevents fertilization, while the hormonal IUD thickens cervical mucus and thins the uterine lining.
These mechanisms are less effective at preventing a fertilized egg from implanting outside the uterine cavity, such as in the fallopian tube. When contraceptive failure happens, the ratio of pregnancies is skewed away from a normal, intrauterine pregnancy. For those who become pregnant while using a copper IUD, approximately 15% of those pregnancies will be ectopic.
The relative risk is higher with hormonal IUDs; about 50% of pregnancies that occur are ectopic. This statistical shift is caused by the device’s high effectiveness in preventing uterine implantation. Despite this elevated relative risk, the overall incidence of ectopic pregnancy in IUD users remains very low.
Recognizing Warning Signs
Recognizing the specific symptoms of an ectopic pregnancy is important, as this condition can become life-threatening without prompt medical intervention. Early signs may be subtle and can mimic a normal early pregnancy, including a missed menstrual period, breast tenderness, or nausea. More concerning symptoms typically appear around six to eight weeks after the last normal menstrual period.
The most common warning signs include severe abdominal or pelvic pain, often localized to one side. This pain can be sharp, dull, or crampy and may be persistent or worsen over time. Abnormal vaginal bleeding or spotting that differs from a normal menstrual flow is another frequent symptom, ranging from light spotting to a heavier discharge.
A less common sign is referred shoulder pain, which results from internal bleeding irritating nerves under the diaphragm. Other indicators of a medical emergency include dizziness, lightheadedness, weakness, or fainting, which signal substantial internal blood loss and shock. Any person with an IUD who suspects pregnancy and experiences these symptoms must seek immediate medical care.
Diagnosis and Necessary Action
A healthcare provider begins diagnosis by evaluating symptoms and performing blood tests to measure human chorionic gonadotropin (hCG). This hormone is monitored over a 48-hour period. A healthy intrauterine pregnancy shows a rapid increase in hCG levels, while an ectopic pregnancy often presents with levels that rise slowly, plateau, or decline.
A transvaginal ultrasound allows the provider to visualize the uterus and surrounding areas. The goal is to confirm the location of the gestational sac. The absence of a sac in the uterus combined with a mass in the fallopian tube confirms an ectopic pregnancy. If the location cannot be definitively confirmed, it is classified as a pregnancy of unknown location, requiring close follow-up.
Timely treatment is essential to prevent fallopian tube rupture, which can cause severe internal hemorrhage. Treatment options depend on the diagnosis timing, patient stability, and whether rupture has occurred. For an early, unruptured ectopic pregnancy in a stable patient, medical management with an injection of Methotrexate may be used to stop cell growth.
If the pregnancy is more advanced or the fallopian tube has ruptured, immediate surgical intervention is required. This procedure is typically performed laparoscopically. The surgeon may perform a salpingostomy, removing the ectopic pregnancy while repairing the tube, or a salpingectomy, removing the entire affected fallopian tube to stop bleeding.