Preconception diet quality and modified natural cycle in vitro fertilisation outcomes

Lifestyle has been associated with in vitro fertilisation (IVF) success rates, but studies on diet and IVF outcomes are inconclusive. We studied associations between adherence to the Dutch guidelines for a Healthy diet 2015 and pregnancy chances among women receiving modified natural cycle in vitro fertilisation (MNC-IVF). This prospective cohort study utilised data from 109 women undergoing MNC-IVF between 2014 and 2018 at University Medical Centre Groningen enrolled in a study examining associations between metabolic profile of follicular fluid and oocyte quality. Adherence to dietary guidelines was assessed by daily food records quantified based on the Dutch Healthy Diet (DHD) 2015 Index. IVF outcomes (i.e. positive pregnancy test, ongoing pregnancy, and live birth) were obtained from patient records. Statistical analyses involved Cox proportional hazard regression analyses while adjusting for maternal covariates age, smoking, and Body Mass Index (BMI), and stratified for treatment, age, BMI, and energy intake. Women were 31.5 ± 3.3 years old, and had a BMI of 23.5 ± 3.5 kg/m². Higher DHD2015 adherence was linked to a reduced probability of achieving an ongoing pregnancy (HR = 0.77, 95%CI: 0.62-0.96), live birth (HR = 0.78, 95%CI: 0.62-0.98), and showed a non-significant trend towards a lower probability of a positive pregnancy test (HR = 0.85, 95%CI: 0.71-1.01). Associations were particularly present among women undergoing MNC-ICSI (n = 87, p-for-interaction = 0.06), with shorter duration of infertility (n = 44, p-for-interaction=0.06), being overweight (n = 31, p-for interaction = 0.11), and having higher energy intakes (n = 55, p-for-interaction = 0.14). This explorative study suggests inverse trends between DHD2015 adherence and MNC-IVF outcomes, encouraging well-powered stratified analyses in larger studies to further explore these unexpected findings.