How Fibroids Affect Fertility: Location, Not Size

The ones that touch or push into the cavity where an embryo has to implant. Fibroids sitting on the outside of the uterus have no measurable effect on fertility, however large they look on a scan. Fibroids inside the muscle wall sit in between: they are associated with lower pregnancy and live birth rates, and taking them out does not fix that.

So "I have fibroids" is not a fertility diagnosis. "I have a fibroid distorting the cavity" is one, and "I have a 7 cm fibroid on the outer surface" mostly is not. Most women with fibroids are not infertile because of them: they are present in roughly one in ten to one in twenty women being investigated for infertility, and are the only cause found in a small fraction of those.

Ask for the FIGO number. Since 2011 fibroids have been classified 0 to 8 by their relationship to the lining and the outer surface, and it is the only description that carries any prognostic information:

• Type 0 — entirely inside the cavity, attached by a stalk, with no muscle involvement.
• Type 1 — submucosal, less than half of its mean diameter inside the muscle.
• Type 2 — submucosal, at least half inside the muscle, focally distorting the cavity.
• Type 3 — abuts the lining but does not focally distort the cavity. This is the borderline category, and the 2018 FIGO revision says it is distinguished from type 2 only at hysteroscopy performed with minimal intrauterine pressure.
• Type 4 — entirely within the muscle wall, touching neither lining nor serosa.
• Types 5, 6 and 7 — subserosal, mirroring 2, 1 and 0: at least half inside the muscle, less than half, and pedunculated on the outside.
• Type 8 — other, typically entirely cervical, and also the detached "parasitic" fibroid.
• Hybrids get two numbers. A fibroid touching both lining and serosa is written as, for example, 2-5. Types 3-5 are also common.

The imaging that gets you there: transvaginal ultrasound first, which finds fibroids reliably but cannot always tell a type 2 from a type 3. Adding saline or gel into the cavity — sonohysterography — is near-perfect for submucosal fibroids specifically and can substitute for diagnostic hysteroscopy. MRI is the most accurate and the most expensive, and is mainly used for surgical mapping. One caution worth carrying into the appointment: only 23% of 1,500 ultrasound reports audited across 19 centres met all the recommended reporting quality criteria. If your report does not state type, size, number and position, it has not told the surgeon what they need.

It depends entirely on the type, and the answer is less certain than surgical practice suggests.

• Submucosal — probably yes, on weak evidence. The observational picture is consistent: pregnancy and implantation rates are lower with a submucosal component and removal looks beneficial. The randomised picture is one trial of 94 women with otherwise unexplained subfertility, where hysteroscopic removal gave a clinical pregnancy odds ratio of 2.44 with a confidence interval running from 0.97 to 6.17 — just short of significance — graded very low quality, and no live-birth data at all. Removal is still the reasonable thing to do for a type 0, 1 or 2 fibroid in someone trying to conceive. The reason is the mechanism and the consistency of the observational data, not a trial that settled it.
• Intramural — no. A 2024 systematic review pooled the comparison directly: myomectomy for intramural fibroids gave a clinical pregnancy odds ratio of 1.10, with a confidence interval from 0.77 to 1.59, against leaving them in place. The same review found that even fibroids under 3 cm were associated with lower pregnancy rates, while fibroids over 5 cm were not significantly different from none — so the intuition that bigger is worse does not hold, and the intuition that removal reverses the association does not hold either.
• Subserosal — no. No difference in fertility outcomes to begin with, and no benefit from removal.
• More than one fibroid — a separate signal. A single fibroid in any location showed no difference in outcomes. Having more than one was associated with lower clinical pregnancy and lower ongoing pregnancy or live birth. Number appears to matter independently of type.

Cochrane's assessment of the whole surgical question is blunt: four randomised trials, 442 participants, very low-quality evidence, only one of which compared myomectomy with no myomectomy at all. It also found no evidence that laparoscopy beats laparotomy, or that one electrosurgical system beats another, for live birth, pregnancy or miscarriage. When a surgeon tells you the approach matters for your fertility, that is an opinion, not a finding.

On this topic the list of things that are not known is longer than the list of things that are, and most of it is sold anyway.

• That uterine artery embolisation is fertility-sparing. This is the claim most worth pushing back on. A systematic review of 17 studies in 989 patients found pregnancy rates lower and miscarriage rates higher after embolisation than after myomectomy — the single randomised trial in it reported a miscarriage rate of 64% — and rated the evidence very low quality. The FEMME trial randomised 254 women and recorded 12 pregnancies after embolisation versus 6 after myomectomy over four years, hazard ratio 0.48 (95% CI 0.18-1.28), with no difference in ovarian reserve hormones; it was not designed to answer the fertility question. A separate meta-analysis of six studies in 353 women found no significant change in AMH or FSH after embolisation, with a fall in antral follicle count at three months in two small studies. Where pregnancy is the goal, myomectomy is the studied option. Embolisation is neither proven safe for fertility nor proven harmful, and that uncertainty is the finding.
• That MR-guided focused ultrasound preserves fertility. No fertility outcome evidence for it was retrieved for this page, so this page makes no claim either way.
• That diet, supplements or herbal remedies shrink fibroids or restore fertility. Nothing retrieved here supports it. Claims about "liver support" or "hormone balancing" have no basis in the sources on this page.
• That fibroids stop ovulation. No retrieved source supports fibroids causing anovulation. Fibroid-related bleeding typically occurs in regular, ovulatory cycles.
• That size is what matters. The 2024 data run the other way for intramural fibroids: small ones were associated with lower pregnancy rates and large ones were not significantly different. Position relative to the lining is the variable with the evidence.
• That the submucosal case is settled. It rests on one small randomised trial that did not reach significance and reported no live births. It is the best-supported operation on this page and it is still very low-quality evidence.

A fibroid on a scan report is not an instruction to operate. These are the questions that decide it.

1. What is the FIGO type, and if it is reported as type 2 or 3, how was that distinguished? The distinction is made at hysteroscopy, not on ultrasound.
2. How many fibroids are there? Number carries its own association, independently of type.
3. Is there any other explanation for not conceiving — tubes, sperm, ovulation, age, time trying? Fibroids are the sole identifiable cause in a small minority of infertile patients, and operating on a fibroid while a tubal or sperm factor goes unaddressed costs time you do not get back.
4. If an intramural myomectomy is proposed, what live-birth benefit is being claimed, and from which study? The pooled answer is no benefit.
5. If embolisation is proposed and you want to conceive, why that rather than myomectomy?
6. If heavy bleeding rather than infertility is the main problem, is this a bleeding decision being presented as a fertility decision? They have different thresholds.

That last point has an Indian edge. A systematic review of 89 hysterectomy audits published between 2010 and 2024 found fibroids and abnormal uterine bleeding to be the leading indications, that about a quarter of hysterectomies were performed in women under 40, and that ovaries were frequently removed without documented pathology. If a hysterectomy is proposed and you have not finished having children, that is the moment for a second opinion rather than a consent form. Being told you have fibroids at 29 and hearing the word hysterectomy in the same conversation is frightening, and in a large share of cases it is also premature.