Preconception dietary patterns and time-to-conception in the high-income multi-country NiPPeR study

BACKGROUND: Dietary patterns rich in plant-based foods, fish, and healthier fats are reportedly beneficial for fertility, but forming generalizable recommendations has been hindered by the lack of studies examining dietary patterns and time-to-conception (TTC) in cohorts with different ethnicities across geographical regions. To study the association of preconception dietary patterns with TTC in the multi-country NiPPeR trial. METHODS: This study is a secondary analysis of data collected in the NiPPeR randomized controlled trial. Women planning to conceive, without known fertility impairment, were recruited from the community in the UK, Singapore, and New Zealand (NZ). Dietary intake was assessed at preconception prior randomization, and across-site (“pooled”) data-driven dietary patterns were derived (n = 1406). TTC, derived as the number of days between recruitment and the estimated date of achieving a clinical pregnancy, and the chance of achieving a clinical pregnancy within a year, expressed as hazard ratios (HR), were analyzed using Cox proportional hazards models adjusted for preconception body mass index, age and gravidity. RESULTS: Two pooled dietary patterns were identified: “Vegetables, Fruits and Nuts” (VFN), and “Fried potatoes, Processed meat and Sweetened beverages” (FPS). Compared with the lowest quartile of VFN score, those in the highest quartile took a shorter time to conceive [Days till 20% conceived (95% CI): 73.0 (60.6, 91.5) vs 166.5 (120.0, 229.5)], and showed a higher chance of conception within a year [HR (95% CI): 2.15 (1.66, 2.78)]. This difference was most evident in Singapore, where the overall adherence to a VFN diet was substantially lower than in the UK and NZ [median (IQR) VFN score (expressed as standard deviation scores): Singapore -0.88 (-1.11, -0.57), UK 0.45 (0.07, 0.92), NZ 0.47 (-0.02, 0.90)]. There was no association between the FPS diet and TTC in the cohort. CONCLUSION: Consuming a diet rich in vegetables, fruits and nuts may shorten TTC and improve the chances of conception, particularly in populations with low intakes of such foods. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02509988, Universal Trial Number U1111-1171–8056. Registered on 16 July 2015.