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How can uterine fibroids interfere with implantation or block sperm from reaching an egg?

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Diagram showing the female reproductive system with labeled ovaries, fallopian tubes, uterus, and vagina, alongside hormone pathways and the process from ovulation to fertilization and early embryo development. — infertility Major structures and hormones involved in the initiation of pregnancy. Also seen, at right, is the development of an egg cell (ovum) from follicle to embryo.

Uterine fibroids, also known as uterine leiomyomata, are benign tumours that develop from smooth muscle cells within the wall of the uterus. These growths can contribute to infertility through two primary mechanisms:21

Interference with Implantation: Fibroids can disrupt the environment of the uterus, which may interfere with the successful implantation of a fertilized egg. In some cases, if a fibroid protrudes into the endometrial cavity, surgical excision may be required to address this issue.21
Obstruction of Sperm: Fibroids can exert physical pressure on the opening of the fallopian tubes. This compression can block the path, preventing sperm from reaching the egg for fertilization.21

The impact of these tumours on fertility often depends on their specific size and location within the uterine structure.1