Many UK clinics still use BMI thresholds to decide who can access IVF. A 2024 review across 32 providers found High BMI cutoffs ranged from 29.9 to 40, with NHS-funded patients facing stricter limits than private care at the very same clinics.
These policies affect access for an estimated 44% of UK women of reproductive age with BMI over 30.
The Human Fertilisation and Embryology Authority also clarifies there is no legal BMI limit in the UK; clinics set their own policies based on clinical judgment.
What the evidence actually says
NICE guidance notes that higher BMI can be associated with longer time to conceive and recommends weight loss for people who are not ovulating, but it does not say BMI should be a hard barrier to fertility treatment. NICENCBI Ethical analysis published in Human Reproduction Open argues that denying IVF solely on BMI is not justified when patients are informed of risks and involved in shared decisions.
The Current Landscape in the UK
A 2024 study presented at the Fertility Congress and conducted at Avenues London, revealed significant inconsistency in BMI cutoffs across UK fertility providers. Data from 32 UK clinics showed:
- BMI eligibility thresholds ranged from 29.9 to 40
- 57% of clinics used BMI <35 as a cutoff
- NHS-funded patients faced stricter limits (mean cutoff BMI 31) than private patients (mean cutoff BMI 36), even within the same clinic
- All 42 Integrated Care Boards (ICBs) that published criteria required BMI between 19 and 30 at referral or treatment initiation
These policies affect access for an estimated 44% of UK women of reproductive age who have a BMI over 30, despite many being healthy and otherwise eligible for care.
Avenues’ Own Research: AI-Powered Oocyte Quality Assessment of High BMI patients
Avenues recently conducted a retrospective study using CHLOE-OQ, an AI-powered tool developed by Fairtility Ltd, to assess oocyte quality (OQ) in relation to BMI.
- Sample: 580 oocytes from 148 patients
- BMI Groups: Normal (<25), Overweight (25–29.9), Obese (30–39.9)
Findings:
- ANOVA testing revealed a statistically significant difference in OQ by BMI group (F=4.23, p=0.015)
- Tukey’s post-hoc analysis showed a significant reduction in OQ for obese vs normal BMI (p=0.021)
- No significant difference between normal and overweight (p=0.602) or overweight and obese (p=0.163)
Interpretation: The data suggests a threshold effect rather than a linear decline in oocyte quality with increasing BMI. This implies that BMI is not a reliable continuous predictor of oocyte quality, and that many patients above a BMI of 30 can still produce high-quality eggs.
Broader Evidence: Ethical and Clinical Considerations
A 2017 review published in Human Reproduction Open evaluated the common justifications for excluding patients with high BMI from fertility care, finding them ethically and medically flawed.
- Risk to the Woman: While pregnancy complications such as gestational diabetes and preeclampsia are more common in patients with obesity, they are not unique to this group. Women with diabetes or other high-risk conditions are not excluded from IVF on that basis.
- Risk to the Child: While certain congenital risks may be elevated, the absolute risks remain low. The threshold of “serious harm” used in reproductive ethics is not met.
- Cost to Society: Although some studies report increased cost per live birth in patients with higher BMI, others show no significant cost difference. More importantly, excluding treatment based on resource allocation alone raises ethical concerns, particularly when similar or higher-risk groups are not similarly excluded.
The authors conclude that denying IVF solely on the basis of BMI is unjustified and discriminatory, particularly when patients are informed of risks and engaged in shared decision-making.
Why Avenues Does Not Use BMI as a Gatekeeper to IVF care
At Avenues, we assess each patient’s fertility potential based on a personalised, AI-driven profile that includes hormonal markers, reproductive history, uterine and ovarian imaging, lifestyle data, and metabolic health, not BMI alone.
We believe this approach is:
- More predictive of success
- More ethical, respecting patient autonomy and equity
- More inclusive, aligned with public health goals to reduce inequities in access
Patients with higher BMI often face bias and exclusion across the fertility sector. At Avenues, we treat people, not numbers, and apply the best available science to optimise every individual’s chance of success.
Our Clinical Outcomes
Avenues’ egg freezing and thaw outcomes, fertilisation rates, and blastocyst development rates consistently outperform national benchmarks.
- Egg survival rate post-thaw: 97%
- Blastocyst development: 78%
- IVF fertilisation rate: 93%Final Avenues Booklet
Our AI-powered tools (including CHLOE OQ, EQ, and IVF 2.0) allow us to personalise care with unmatched precision, enabling more patients, including those with high BMI, to achieve successful outcomes.
Patients deserve options, not obstacles
Research in 2024 documented the harms of BMI-based NHS funding restrictions, from delayed care to emotional distress. BioMed Central At Avenues, we replace exclusion with informed choice, clear conversations about risk, and AI-supported precision throughout care.
Introducing Fair IVF+
If you were told your BMI makes you ineligible, you can now choose Fair IVF+, our BMI-inclusive pathway that keeps the transparent, all-in structure of Fair IVF and adds tailored peri-operative planning and dosing for HBMI profiles.
This is the first truly accessible IVF package for high BMI Patients.
Two options are available:
- Fair IVF+ (Core). Everything in Fair IVF, plus anaesthesia and dosage support, and adjusted protocols when indicated. For £4,349.
- Fair IVF+ with Coaching by Nicola Salmon. Core package plus three 1:1 sessions with the Fat Positive Fertility Coach focused on advocacy and confidence. For £4,949.
Learn more about the Fair IVF+ Package here!
Citations:
HFEA – Are there BMI limits in UK law? https://www.hfea.gov.uk/contact-us/frequently-asked-questions/
NICE guideline CG156 – Fertility problems: assessment and treatment (PDF) https://www.nice.org.uk/guidance/cg156/resources/fertility-problems-assessment-and-treatment-35109634660549
Royal College of Anaesthetists – Anaesthesia and your weight https://www.rcoa.ac.uk/patients/patient-information-resources/patient-information-leaflets-video-resources/anaesthesia-your-weight
RCOG – Care of Women with Obesity in Pregnancy (Green-top 72) https://www.rcog.org.uk/guidance/browse-all-guidance/green-top-guidelines/care-of-women-with-obesity-in-pregnancy-green-top-guideline-no-72/
Reproductive Health (2024) – Harms of BMI-based NHS IVF restrictions https://reproductive-health-journal.biomedcentral.com/articles/10.1186/s12978-024-01891-1
