The Effects of Uterine Fibroids on Pregnancy in Women

Infertility is defined as the inability of a couple to achieve pregnancy over an average period of one year of unprotected sexual intercourse. Currently, one in six couples is affected by infertility worldwide. With the development of society bringing enormous material and spiritual wealth to human beings, comprehensive factors such as environmental pollution, life and work pressure and bad habits have an important impact on fertility. Infertility is a disease that seriously affects the physical and mental health of patients and brings about serious social problems. According to the World Health Organization (WHO), infertility will become the third major disease in the 21st century following tumor and cardiovascular diseases. Infertility can be caused by a single factor or multiple factors together. The WHO proposed a classification method based on etiological diagnosis to classify infertility into six major causes: ovulation factors, fallopian tube problems, uterine factors, cervical factors, male factors and psychosocial factors. There is a serious impact on female fertility due to heredity, auto-immunity, infection, metabolic abnormalities, surgery and other factors. The main factors leading to female infertility include patient age, education level, weight (obesity), menstrual history (irregular menstrual cycle), pregnancy history (stillbirth and abortion history), disease history (ovarian cyst, ovarian aging, endocrine autoimmune diseases, fallopian tube abnormalities, pelvic abnormalities and uterine abnormalities), sexual history, previous surgical history, smoking history, chemical exposure history, and mental stress, etc. The objective of this study is to explore the impact of uterine fibroids on female pregnancy rate. Uterine fibroid is a common benign tumor of female reproductive tract, with 25% to 50% of women of childbearing age suffering from uterine fibroid. The fibroids can cause various clinical symptoms, including menorrhagia, prolonged menstruation, pelvic compression and pain, as well as infertility and obstetric complications, but mostly are asymptomatic. The prevalence of fibroids increases with the age of women, while the fertility rate declines with ages. This complex relationship is particularly harmful. The mechanisms related to fibroids and infertility vary with the type and location of fibroids, including anatomical structure deformation, and interference with the physiological changes of endometrium and implantation of zygotes. In addition, fibroids can destroy the anatomical structure of the pelvis and disrupt the function of the fallopian tube. The FIGO classification describes nine types of fibroids: submucosal fibroids (type 0, Ⅰ, Ⅱ), intramural fibroids (types Ⅲ, Ⅳ, Ⅴ), and subserous fibroids (types Ⅵ and Ⅶ). Among them, submucosal and some intramural fibroids can lead to endometrial inflammatory environment, affecting sperm migration and embryo implantation. Nevertheless, there is still controversy in epidemiological studies regarding the relationship between uterine fibroids and female infertility. Parity has a significant protective effect against fibroid development, and in fact infertile women may be at higher risk for fibroids. Similarly, it is difficult to distinguish whether fibroids have a direct deleterious effect on infertility, or whether the fibroid-infertility association is mediated by concomitant factors that affect fertility. In addition, the impact of each type of fibroids on fertility varies by the difference in the number, size, and location of fibroids, and the combinations of different fibroids may have special effects. Do uterine fibroids already exist when women plan and attempt to conceive? Do uterine fibroids have negative effects on fertility during this period? It is an urgent need to solve this problem at the present. Therefore, this study is of great significance for us to understand the impact of fibroids on female fertility and guide the treatment patterns of female patients with uterine fibroids who have fertility needs.