Maternal Methyl-Group Donor Intake and Neonatal Birth Size in Singleton IVF Pregnancies

Background/Objectives: Maternal intake of methyl-group donors (MGD) during pregnancy may influence fetal development, yet its role in in vitro fertilization (IVF) pregnancies remains poorly understood. The aim of the present study was to investigate maternal intake of MGDs during late pregnancy and its association with neonatal outcomes in IVF versus spontaneously (S) conceived pregnancies. Methods: We assessed third-trimester, daily maternal intake of MGD (folate, betaine, choline, methionine, and folic acid) using a validated food-frequency questionnaire, and maternal supplement intake using a structured questionnaire. Methyl-donor nutrient score (MDNS) was calculated based on deciles of MGD intake. Serum folic acid and vitamin B12 concentrations were measured using standardized immunochemical assay. Predefined inclusion and exclusion criteria were applied. Anthropometric data were measured from singleton newborns (weight, length, head- and waist circumference, body composition) and mothers (height, weight, body composition) after delivery. Statistical analysis was conducted using R (4.1.2v). Results: 265 mother–child pairs were included in the study (IVF n = 83). Daily dietary intake of MGDs was similar between groups, but IVF mothers reported significantly higher daily folic acid (668.7 ± 1050.9 vs. 418.8 ± 419.2 µg, p = 0.0034) and vitamin B12 (11.07 ± 31.58 vs. 7.95 ± 29.00 µg, p = 0.0078) supplementation. Serum analyses were available in a subgroup (n = 131, IVF n = 61) of mothers, showing higher postpartum folate (IVF: 10.96 ± 5.54 vs. S: 8.29 ± 4.72 µg/L, p = 0.0064) and vitamin B12 (IVF: 288.22 ± 113.82 vs. S: 233.70 ± 78.23 ng/L, p = 0.0053). Maternal daily dietary choline intakes were significantly below recommendations (IVF: 251.9 ± 98.5 mg, S: 243.8 ± 106.8 mg). Among 151 singleton neonates (IVF n = 57), anthropometric parameters did not differ between IVF and spontaneously conceived groups and were not associated with MDNS tertiles. Conclusions: Maternal MGD intake during third trimester of pregnancy was not associated with neonatal anthropometric outcomes in singleton pregnancies. Consistently low dietary choline intake highlights a potential nutritional gap warranting improved dietary guidance and supplementation strategies.