Uterine Fibroids & Fertility

The impact of uterine fibroids on fertility depends primarily on their location and size, not their mere presence. Submucosal fibroids (FIGO type 0, 1, and 2 — projecting into or distorting the uterine cavity) have the greatest detrimental effect. They impair fertility through multiple mechanisms: mechanical obstruction of the tubal ostia, disruption of normal sperm transport, alteration of normal uterine contractility, impairment of implantation through altered endometrial vascularity and molecular signaling (reduced HOXA10 and LIF expression), and increased early pregnancy loss. A systematic review by Pritts et al. (Fertil Steril 2009) found that submucosal fibroids reduced implantation rates by 50–60% and live birth rates by approximately 70% — a clinically dramatic effect that is largely reversible with myomectomy.

Intramural fibroids (FIGO type 3–5, within the myometrium without cavity distortion) have a more variable and debated impact. Current evidence, including a meta-analysis by Somigliana et al. (Hum Reprod Update 2016), suggests that intramural fibroids ≥ 4 cm are associated with significantly reduced implantation and live birth rates in IVF, even without overt cavity distortion on 2D ultrasound. Proposed mechanisms include altered uterine peristalsis, reduced subendometrial vascularity, and mechanical pressure effects. For smaller intramural fibroids (< 4 cm) not abutting the cavity, current evidence does not support routine myomectomy before IVF, and the surgical risks may outweigh uncertain benefits. This remains an area of active clinical debate.

Subserosal fibroids (FIGO type 6–7, projecting outward from the uterus) have minimal impact on intrauterine fertility unless very large and compressing the fallopian tubes externally. They are rarely treated for reproductive purposes. Pedunculated subserosal fibroids occasionally undergo torsion and may be removed laparoscopically for symptomatic reasons. When multiple fibroid types coexist — a common finding — the clinical decision centers on the most impactful lesion, typically the submucosal or large intramural fibroid. MRI is the gold-standard imaging modality for fibroid mapping, providing superior characterization of fibroid number, location, size, and relationship to the endometrial cavity compared to ultrasound.