In vitro fertilization (IVF) is a medical treatment that involves carefully controlled hormonal stimulation of the ovaries to assist in conception. Uterine polyps, also known as endometrial polyps, are common growths on the inner lining of the uterus. A frequent concern for individuals undergoing fertility treatment is whether the intensive hormonal protocols of IVF might increase the risk of developing these polyps.
Defining Uterine Polyps
Uterine polyps are localized, typically non-cancerous overgrowths of the endometrial tissue, which lines the uterus. These growths contain endometrial glands, fibrous connective tissue, and blood vessels. They can range in size from a few millimeters up to several centimeters. They attach to the inner uterine wall by either a broad base or a slender stalk and protrude into the uterine cavity.
Polyps are a common finding, frequently occurring in women of reproductive age, even outside of fertility treatments. The most common symptom associated with endometrial polyps is abnormal uterine bleeding. This can manifest as irregular or heavy menstrual periods, or spotting between cycles. Although many polyps are asymptomatic, their presence is often investigated in patients experiencing difficulty with conception.
The Hormonal Link Between IVF Treatment and Polyp Growth
Endometrial polyps are highly dependent on estrogen for their growth and development. While the exact cause of polyp formation is not fully known, hormonal factors play a significant role. Polyps are rarely observed before menstruation and their growth is often linked to an environment of estrogen stimulation.
The ovarian stimulation phase of an IVF cycle requires administering high doses of exogenous hormones, such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). This encourages the development of multiple egg follicles, creating a temporary state of hyper-estrogenism. Circulating estradiol levels become significantly higher than in a natural cycle, promoting the rapid proliferation of the endometrial lining.
This intense growth stimulation can trigger the excessive and localized proliferation of endometrial cells in some individuals, leading to the formation or accelerated growth of polyps. While IVF does not directly cause the condition, the pharmacological agents used create a hormonal environment that is conducive to polyp growth. Medical consensus views this relationship as a strong correlation, where the IVF protocol acts as a powerful growth promoter in a susceptible uterine environment.
Screening and Detection During the IVF Process
Because uterine polyps can negatively affect the success of fertility treatments, screening the uterine cavity is a routine part of the IVF process. The constant monitoring required for IVF often leads to the detection of polyps earlier than in the general population.
These detection methods are typically performed during the preliminary workup phase, before ovarian stimulation begins, or prior to a frozen embryo transfer cycle. Identifying polyps at this stage allows the fertility specialist to address them before significant time and resources are invested in an unsuccessful embryo transfer. The timing of the screening ensures that the uterine environment is optimized for subsequent implantation attempts.
Detection Methods
The primary non-invasive screening method is a Transvaginal Ultrasound (TVS), which can identify a thickening or irregularity in the endometrial lining. To gain a clearer picture, Saline Infusion Sonography (SIS), also called a hydrosonography, is often utilized. This procedure involves injecting sterile saline solution into the uterine cavity during a TVS to expand the space, allowing polyps to be clearly outlined against the fluid. The gold standard for confirming the diagnosis is a diagnostic Hysteroscopy, where a thin scope is inserted through the cervix to allow direct visualization of the cavity.
Impact of Polyps on Implantation Success
The presence of polyps can significantly interfere with the success of an IVF cycle and the patient’s ability to achieve a viable pregnancy. Polyps interfere through both mechanical and biochemical mechanisms.
Mechanical Interference
A polyp acts as a space-occupying lesion, disrupting the smooth surface of the endometrial lining. This physical barrier can prevent the embryo from properly attaching to the uterine wall. This is especially true if the polyp is large or located near the fundus, which is the preferred implantation site.
Biochemical Interference
Polyps negatively affect uterine receptivity by inducing localized inflammatory changes within the endometrium. This can create an environment hostile to the implanting embryo. Furthermore, polyps may produce substances, such as the glycoprotein glycodelin, which can render the uterine lining less receptive to the embryo.
Due to these detrimental effects on implantation and clinical pregnancy rates, medical guidelines generally recommend the surgical removal of polyps through hysteroscopic polypectomy before proceeding with embryo transfer. Studies have shown that removing polyps, especially those over 10 millimeters, can significantly improve clinical pregnancy and live birth rates in women undergoing IVF. Removing the polyp restores the integrity and functionality of the endometrial lining, maximizing the chances for a successful outcome.