Intrauterine devices (IUDs) are a highly effective, long-acting, and reversible form of contraception; fertility returns quickly upon removal. The two main types, hormonal and copper IUDs, prevent pregnancy through different mechanisms, which is significant when considering fertility testing. Assessing future fertility while the device is still in place can be complex because the IUD’s localized actions may interfere with certain diagnostic tests. Understanding how each device interacts with the reproductive system is key to determining the accuracy of any fertility assessment performed.
How IUDs Affect the Reproductive System
The two types of IUDs prevent conception through distinct biological pathways. The copper IUD is non-hormonal, using a small copper coil that releases copper ions into the uterine cavity. These ions create a local inflammatory reaction toxic to sperm, preventing fertilization. Because this mechanism is non-hormonal, the device does not interfere with the natural hormonal cycle or suppress ovulation.
The hormonal IUD releases a synthetic progestin hormone directly into the uterus. This localized hormone primarily works by thickening the cervical mucus, impeding sperm from reaching the egg. The progestin also thins the uterine lining, making it unsuitable for implantation. Although the hormone is largely localized, it can sometimes suppress or alter the pattern of ovulation, particularly with higher-dose devices, which affects systemic hormone markers.
Accuracy of Fertility Tests When the IUD is Present
The presence of an IUD can mask or alter the results of standard fertility assessments, depending on the test’s focus and the type of IUD used. These tests generally assess either the ovarian reserve or the function of the menstrual cycle. It is important to differentiate the effects created by the hormonal versus the copper IUD types.
Ovarian Reserve Markers
Tests that measure ovarian reserve, such as the Anti-Müllerian Hormone (AMH) test, are generally reliable regardless of IUD type. AMH is produced by small follicles in the ovaries and indicates the remaining egg supply. Although some studies suggest hormonal IUDs may temporarily lower AMH levels slightly, the results are usually close enough to the true baseline to be clinically useful for assessing overall egg quantity. Since the copper IUD does not affect hormone levels, AMH and Follicle-Stimulating Hormone (FSH) tests are completely accurate while it is in place.
Hormonal Cycle Tracking
Hormone-based tests used to confirm or track ovulation are less reliable when a hormonal IUD is present. A progesterone test, performed midway through the luteal phase, measures the hormone spike confirming recent ovulation. For hormonal IUD users, ovulation may be suppressed or irregular. Therefore, a low progesterone level may reflect the contraceptive action rather than a baseline fertility issue. Conversely, because the copper IUD does not suppress the hormonal cycle, tests for Luteinizing Hormone (LH) and progesterone are accurate for tracking ovulation in these users.
Uterine and Endometrial Assessment
Any assessment of the uterus or uterine lining for implantation readiness is misleading while an IUD is in place. The hormonal IUD intentionally thins the endometrium, and the copper IUD causes a localized, sterile inflammatory response. An ultrasound or imaging technique assessing the lining’s thickness and appearance will show a condition directly resulting from the contraceptive action. This assessment provides no meaningful information about the uterus’s capacity to support a pregnancy after the device is removed.
Fertility Assessment After IUD Removal
IUDs do not cause long-term fertility suppression. Fertility returns almost immediately after removal, regardless of whether the device was hormonal or copper. For users of a copper IUD, the natural cycle was never interrupted, so the return to full fertility is instantaneous.
The body may need a brief adjustment period after a hormonal IUD is removed since the localized progestin is no longer present. However, a regular menstrual cycle and ovulation typically return within the first month. Most medical guidelines recommend that couples under the age of 35 attempt to conceive for 12 months before seeking further fertility testing.
If a couple has not conceived after this standard period, a full fertility workup is recommended. At this point, testing—including hormonal blood work and structural assessments—will accurately reflect the body’s natural reproductive function, as the IUD is no longer a confounding factor. The IUD itself is not a cause of infertility, and any issues discovered during a post-removal workup are generally due to underlying factors unrelated to the device’s previous use.