If you are considering an IUD—or have one already—you may be wondering how effective they are at preventing pregnancy. Here is what you need to know about IUDs, including the chances of getting pregnant while using one, as well as the associated risks if pregnancy were to occur.
What Is an IUD?
An IUD is a tiny device that’s inserted in the uterus to prevent pregnancy, says Michael Cackovic, MD, a maternal-fetal medicine specialist and clinical associate professor of obstetrics and gynecology at Ohio State University Wexner Medical Center. “It is a long-term reversible contraceptive device that is one of the most effective birth control methods available,” says Dr. Cackovic. “They are considered to be [more than] 99% effective at preventing pregnancy.” Generally speaking, there are two types of IUDs—hormonal and non-hormonal. Both types work in different ways to make the uterine environment hostile to conception and pregnancy, Dr. Cackovic explains. And while they begin working as soon as they are inserted, they are also immediately reversible, meaning you can get pregnant as soon as your IUD is removed. “IUDs work in a couple of different ways,” says Anita Somani, MD, an OB/GYN with Ohio Health Physician Group. “For instance, the copper IUD, which is non-hormonal, creates a foreign body reaction that thickens the cervical mucous and alters the lining so that it is not able to sustain a pregnancy. Meanwhile, hormonal IUDs make it less likely for you to ovulate.” Research suggests that the IUD’s ability to prevent pregnancy far surpasses other methods of hormonal birth control such as pills, patches, and contraceptive rings. Plus, it has other uses. For instance, the IUD has emerged as a first-line recommendation for people who have heavy menstrual bleeding, pelvic pain, or need to regulate their periods. “The non-contraceptive benefits of an IUD also are very important,” says Dr. Somani. “For instance, it also can be used to treat endometriosis and endometrial hyperplasia and it can help regulate a person’s periods.“Despite these benefits, some people have some misconceptions about how IUDs work. They might falsely fear that IUDs are causing abortions or that they can impact a person’s fertility. “You should not look at an IUD as something that causes abortion,” Dr. Somani adds. “It is not causing abortion, but instead is creating a hostile environment in the uterus. IUDs also are safe and do not cause infertility issues.”
Chances of Pregnancy With an IUD
Although it is extremely rare that an IUD might fail or result in pregnancy, the most likely scenarios involve an IUD being expelled from the uterus or slipping from the uterine canal, says Dr. Cackovic. Another reason for failure might be if the hormonal IUD has expired or needs to be replaced. Additionally, the uterus might have an abnormal shape or could contain a fibroid, which can also be causes for expulsion. “Generally, the expulsion rate is about 5% in the first year and much lower thereafter,” says George Kovalevsky, MD, an OB/GYN and partner at Delaware Institute for Reproductive Medicine. “Although rare, pregnancies can occur with the IUD in place. We don’t know exactly why that happens, but no reversible [birth control] method is perfect.” That said, the chance of getting pregnant with an IUD is extremely rare. In fact, IUDs tend to be more effective than even birth control pills, which can be impacted by human error. For instance, a person can forget to take a pill, or they might take it inconsistently, thereby lowering its efficacy. “With typical use that includes the possibility of human error, the risk of pregnancy with the pill is about 7% to 9%,” confirms Dr. Kovalevsky. “With an IUD, the risk is less than 1%.” In fact, only about 0.2% to 0.8% of patients who use an IUD get pregnant, points out Hongmei Meng, MD, an OB/GYN with Altos Oaks Medical Group at Stanford Medicine Children’s Health.
Risks If Pregnancy Occurs With an IUD
Because IUDs are so effective at preventing intrauterine pregnancies, if a pregnancy does occur, there’s a higher likelihood that it developed outside the uterus. For this reason, if you do become pregnant while using an IUD, you should be evaluated for an ectopic pregnancy. “The chance of getting pregnant with an IUD is rare,” says Dr. Cackovic. “However, if you do get pregnant with an IUD in place, it’s more likely to be ectopic pregnancy as they primarily occur in the fallopian tubes, away from the contraceptive effect of the device.” It also is important to understand that you are not at an increased risk for ectopic pregnancy just because you might have an IUD. Pregnancy, if it does occur, is just more than likely to occur outside the uterus with an IUD. For this reason, you should be evaluated right away if you suspect you are pregnant. “[Ectopic pregnancies] can be very dangerous and cause life-threatening hemorrhage if undiagnosed and untreated,” Dr. Cackovic says. Conversely, if it is an intrauterine pregnancy and not an ectopic pregnancy, it is generally recommended that the IUD be removed, Dr. Cackovic adds. But even after removal, there are some additional risks associated with pregnancy with an IUD. “If there is an intrauterine pregnancy with an IUD in place, there are increased risks for miscarriage, infections such as septic abortion and chorioamnionitis, preterm birth, and abruption,” Dr. Meng says.
What to Do If You Suspect Pregnancy While Using an IUD
If you have an IUD and think you might be pregnant, it is important to take a home pregnancy test. If your test is positive, call your OB/GYN or healthcare provider right away. They can order an ultrasound and perform an exam. In the meantime, if you develop pelvic pain with vaginal bleeding, you should get immediate medical attention to determine if you have an ectopic pregnancy. Ectopic pregnancies can be life-threatening situations and need to be addressed right away. This may mean medication or it may involve surgery, depending on your situation. If ectopic pregnancy occurs, there is a higher risk of rupture and hemorrhage, so you should not delay care if you are pregnant with an IUD. Left untreated, an ectopic pregnancy can cause infection and, in some cases, even death. If your pregnancy test is negative and you are still concerned, be sure to call your healthcare provider. They can answer your questions, perform an exam, and do additional testing. Remember that IUDs are an incredibly effective form of birth control, but no contraceptive is 100% perfect. So, although rare, there is still a very small chance of getting pregnant with an IUD.
A Word From Verywell
IUDs are one of the most effective forms of birth control and the risk of pregnancy when using one is extremely low. If pregnancy does occur, it might be an ectopic pregnancy, which requires medical attention. If you suspect that you are pregnant while using an IUD, it is important to contact your OB/GYN or healthcare provider. They can identify whether it is a viable pregnancy, and talk to you about next steps.
