Intrauterine devices (IUDs) are extremely effective for birth control. A woman who uses an IUD has less than a 1 percent chance of getting pregnant in a year, according to Planned Parenthood. However, when pregnancy does happen despite using an IUD, there can be serious complications to the pregnancy and risks to the mother and the fetus.
When a woman is pregnant with an IUD in place, the likelihood of a miscarriage, vaginal bleeding, placental abruption, which is a separation of the placenta from the uterus before delivery, or premature delivery increase. According to Dr. Sun Kwon Kim and colleagues in the January 2010 issue of Journal of Perinatal Medicine, at least some of these outcomes result from uterine infections that occur more frequently in pregnant women with IUDs. Women who become pregnant while using an IUD also have a greater risk for an ectopic or tubal pregnancy, a potentially life-threatening complication. Dr. Kim’s study concluded that pregnant women with an IUD “are at very high risk for adverse pregnancy outcomes.”
In Dr. Kim’s study of 196 pregnant women with IUDs, 56 percent had a premature baby compared to only 21 percent of the control group, or women pregnant without an IUD. On average, women with an IUD gave birth at 28.5 weeks. Women with an IUD were three times more likely to have a placental abruption. In this study, miscarriages after 12 weeks of pregnancy occurred in 16 percent of women with an IUD, compared to only 1 percent of control women. According to Military Obstetrics and Gynecology, 5 percent of IUD pregnancies implant ectopically outside the uterus, compared to 1 percent of pregnancies without an IUD.
Dr. Kim’s study included women who retained their IUD throughout pregnancy. Military Obstetrics and Gynecology says that early miscarriages occur in half of all women who become pregnant while using an IUD, but the rate drops to 25 percent if a doctor removes the IUD immediately after confirming pregnancy. Planned Parenthood counsels women to have their IUDs removed as soon as they know they are pregnant to lower their risks of serious complications.
The Mirena IUD releases a synthetic hormone called levonorgestrel, similar to the naturally occurring hormone progesterone. This synthetic hormone is often used in birth control pills as well. If a pregnancy occurs while a woman is using the Mirena IUD, the embryo will be directly exposed to levonorgestrel as long as the IUD remains in place. The long-term effects of such exposure on the health of the baby are not known, according to Contracept.org.
Immediate removal of an IUD by a health care provider during early pregnancy is usually straightforward and simple, according to Military Obstetrics and Gynecology. As pregnancy progresses, the removal strings that hang down from the IUD can retract up into the uterus, complicating removal. Contracept.org says that removing an IUD can cause a miscarriage, but retaining the IUD also increases the risk for miscarriage and other complications.