O-302 Impact of personalized nutrition and Lactobacillus crispatus-M247 administration on euploid blastocyst transfer outcomes in patients with unhealthy lifestyles: A matched case-control study

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Abstract Study question Is a personalized nutrition intervention, alongside Lactobacillus crispatus-M247 administration, associated with the live birth rate (LBR) per euploid embryo-transfer in patients with unhealthy lifestyle habits? Summary answer A tailored nutrition program combined with Lactobacillus crispatus-M247 for ≥2months before embryo-transfer improved LBR in patients with unhealthy lifestyle habits (OR: 2.3). What is known already About 50% of euploid blastocyst transfers still do not result in a LB. Increasing evidence suggests that modifiable factors are critical in achieving a successful full-term pregnancy, including maternal nutrition and microbiota. Interestingly, these two factors are closely interconnected. Diet is a major modulator of gut microbiota composition, which in turn influences two important aspects related to the chances of obtaining a LB: the risk of metabolic disorders (e.g., insulin resistance or obesity) and microbiota composition at distal sites such as endometrium and vagina. Study design, size, duration Matched case-control study (2017-2023) including patients with ≥1 euploid blastocyst and ≥1 previous implantation failure all reporting poor adherence to the Mediterranean diet and/or unhealthy lifestyle habits (e.g., smoking, alcohol consumption, limited physical activity) during the consultation. Participants received personalized nutrition plans and underwent Lactobacillus crispatus-M247 supplementation for at least 2 months prior to transfer. Outcomes were compared between 87 patients who declined the intervention and 163 who accepted it. Participants/materials, setting, methods The patients were 37 years old at oocyte-retrieval and 38 at embryo-transfer. The nutritional counseling (including anthropometric measurements and Bioelectrical-Impedance-Analysis [BIA]) highlighted a population with a body composition profile trending toward upper limits of normal (fat-mass 24Kg, waist-circumference 89cm, BMI 23Kg/m2). A modified-natural or hormonal-replacement endometrial preparation was adopted. All euploid blastocysts (52% day5 and 48% day6; 76% AA-quality, 24% AB/BA/BB/AC/CA-quality) were transferred 2hours after warming on a trilaminar endometrium thicker than 7mm. Main results and the role of chance The patients in the control and study groups were similar for all anamnestic, anthropometric, and IVF cycle features, representing two well-matched populations. Also, the euploid blastocysts transferred were similar in terms of day of development and morphological quality. No difference was reported in the two groups in terms of preparation for embryo transfer, except for the administration of Lactobacillus crispatus-M247 and the adherence to a tailored nutrition plan in the study group for ≥2 months (Median:6, Q1:3, Q3:10) before the euploid transfer. The positive pregnancy test rate per transfer was 51% (N = 44/87) versus 69% (N = 112/163; p = 0.004) in the control versus the study group. The biochemical pregnancy loss rate per positive pregnancy test was 14% (N = 6/44) versus 12% (N = 14/112; p = 0.457). The miscarriage rate was 6% (N = 2/36) versus 4% (N = 4/98; p = 0.513). The LBR per transfer was 39% (N = 34/87) versus 58% (N = 94/163; p = 0.004; Power=87%; OR = 2.3, 95%CI:1.2-3.6). The OR was adjusted for the only confounder on the primary outcome, i.e., maternal BMI at transfer (OR = 0.93,95%CI:0.87-0.99). No difference was reported in the gestational age (38±2weeks versus 38±1weeks; p = 0.99) and in the birthweight (3270±450g versus 3306±454g; p = 0.751) of the newborns in the two groups. Limitations, reasons for caution Retrospective study. We could not distinguish Lactobacillus crispatus-M247 from the dietary intervention effects per se. Moreover, metabolic markers and microbiota were not assessed before and after the intervention. Lastly, reliance on self-reported Mediterranean diet adherence and lifestyle introduces potential bias. Wider implications of the findings The study reinforces the importance of nutrition counseling, particularly for patients with unhealthy lifestyle habits prior to embryo transfer. It also highlights the need for prospective investigations into the clinical efficacy of personalized nutrition and gut and vaginal microbiota composition, including potential supplementation to address imbalances. Trial registration number No

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