Adherence to the Mediterranean diet and IVF success rate among non-obese women attempting fertility.

STUDY QUESTION: Is adherence to the Mediterranean diet (MedDiet) associated with better IVF performance in women attempting fertility?

SUMMARY ANSWER: Greater adherence to the MedDiet, defined using the validated Mediterranean diet score (MedDietScore), was associated with a higher likelihood of achieving clinical pregnancy and live birth among non-obese women <35 years of age.

WHAT IS KNOWN ALREADY: Diet impacts fertility and certain nutrients and food groups appear to have a greater effect on reproductive health, but there are relatively few published data on the role of dietary patterns, and the MedDiet in particular, on assisted reproductive performance.

STUDY DESIGN, SIZE, DURATION: This prospective cohort study included 244 non-obese women (22-41 years of age; BMI < 30 kg/m2) who underwent a first IVF treatment in an Assisted Conception Unit in Athens, Greece, between November 2013 and September 2016. The study was designed to evaluate the influence of habitual dietary intake and lifestyle on fertility outcomes.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Diet was assessed before the IVF treatment via a validated food-frequency questionnaire. Adherence to the MedDiet was assessed through the MedDietScore (range: 0-55), with higher scores indicating greater adherence. Intermediate outcomes (oocyte yield, fertilization rate and embryo quality measures) and clinical endpoints (implantation, clinical pregnancy and live birth) were abstracted from electronic medical records. Associations between MedDietScore and IVF outcomes were analysed using generalized linear models adjusting for age, ovarian stimulation protocol, BMI, physical activity, anxiety levels, infertility diagnosis, caloric intake and supplements use.

MAIN RESULTS AND THE ROLE OF CHANCE: No association of MedDietScore with any of the intermediate outcomes or with implantation was found. However, compared with women in the highest tertile of the MedDietScore (≥36, n = 86), women in the lowest tertile (≤30, n = 79) had significantly lower rates of clinical pregnancy (29.1 vs 50.0%, P = 0.01) and live birth (26.6 vs 48.8%, P = 0.01). The multivariable-adjusted relative risk (95% CI) for clinical pregnancy comparing women in the lowest with women in the highest tertile of the MedDietScore was 0.35 (0.16-0.78; P-trend=0.01), and for live birth it was 0.32 (0.14-0.71; P-trend = 0.01). These associations were significantly modified by women's age (P-interaction <0.01 for both outcomes). MedDietScore was positively related to clinical pregnancy and live birth among women <35 years old (P ≤ 0.01) but not among women ≥35 years. Among women <35 years, a beneficial 5-point increase in the MedDietScore was associated with ~2.7 times higher likelihood of achieving clinical pregnancy and live birth.

LIMITATIONS, REASONS FOR CAUTION: Our finding cannot be generalized to the whole reproductive population nor to obese women nor to women attending infertility clinics around the world. In addition, due to the observational study design, causal inference is limited.

WIDER IMPLICATIONS OF THE FINDINGS: The results suggest that diet modifications and greater compliance to the Mediterranean diet may help increase the chances of a successful pregnancy and delivering a live baby for women undergoing IVF treatment.

STUDY FUNDING/COMPETING INTEREST(S): This work was partially supported by a grand from Harokopio University (KE321). All authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER: NCT03050944.