Dr. Lawrence Gugino Responds:
There are very few studies to guide pregnancy outcomes with a pregnancy and IUD. Most studies are from the 1970's and are observational in nature.
The IUD should ideally be removed, but this is sometimes not possible, as in this case. Further attempts at removal would significantly increase the risk of miscarriage. There remains an increased risk of miscarriage with any pregnancy with an IUD.
Other increased pregnancy risks are placenta previa, placental abruption, a low-birth-rate infant, chorioamnionitis (infection), and an increased risk of delivery by cesarean section. Because this IUD is Mirena, which contains a slow release progestin (levonogesterol), there is a theoretical concern of fetal exposure to this progestin. However, the systemic dose released is lower than in the combination oral contraceptive pill, which has shown no teratogenic effect, thus I would doubt there is a significant risk to the fetus.
Surveillance during the pregnancy should include counseling for increased risk of miscarriage and placental abruption later in pregnancy, thus any vaginal bleeding deserves immediate evaluation. There should also be fetal growth surveillance by ultrasound in the third trimester. I would advise that you also be followed by a high-risk maternal fetal medicine specialist, in addition to your general OB/GYN.
– Dr. Lawrence Gugino
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