Aim
To assess the effect of oral complementary and alternative medicine (CAM) on the oocyte, embryo and pregnancy rate in first‐cycle in vitro fertilisation (IVF).

Method
A prospective cohort study using the International CAM Questionnaire, reviewing patient IVF outcomes. Local ethics approval was obtained.

Results
Over 18 months (October 2015 to April 2017) 25 patients were prospectively recruited, with 52% (n = 13) using herbal or dietary supplements, including Chinese medicine, fish oil, liver ‘detox’, co‐enzyme Q10, spirulina, probiotics and maca root. Comparing users to non‐users, there was no statistical difference in age, body mass index, primary infertility, gravidity or parity. Total follicle‐stimulating hormone dose was equivalent (2760 vs 2451 IU, P = 0.60), but there was a significant difference in maximum oestradiol response (4134 vs 8335, P = 0.045), on univariate analysis alone. While no difference was found in the number of follicles >11 mm (7.5 vs 11.5, P = 0.80), or eggs collected (8.0 vs 12.5, P = 0.91), there was a lower number of eggs fertilised in users (3.0 vs 4.0, P = 0.046). There was no difference in the chemical or clinical pregnancy rate.

Conclusion
This small study demonstrates a high use of oral CAM in first‐cycle IVF patients, with a wide range of types. There appears to be a lower fertilisation rate in the women who used oral CAMs. It is unclear whether this is a negative effect of the CAM or selection bias. This concern about confounders supports the need for further research into unregulated herbal medicine on IVF outcomes, given that so many women are using these substances.