OP01.01: *Maternal lifestyle risk factors and human embryonic morphologic development: the Generation R Next study

The rising prevalence of poor lifestyle choices in women of reproductive age poses a significant public health concern, due to implications for fetal growth and long-term health. However, the importance of lifestyle choices on periconceptional health expressed in embryonic development, is still understudied. Our aim was therefore to investigate the association between periconception lifestyle risk factors and human embryonic morphologic development. Within the Generation R Next Study, a population-based periconception cohort study, women with singleton pregnancies underwent serial transvaginal 3D ultrasound scans between 6+0 and 10+2 weeks of gestation. With virtual reality techniques, we evaluated embryonic development using the Carnegie staging system. Stages are based on the external and internal morphological development of the embryo. Information on periconception smoking, alcohol consumption, caffeine use, physical activity and folic acid supplement use was collected via questionnaires. First trimester plasma folate levels were measured. We used linear mixed models to examine the association between lifestyle risk factors and embryonic development. In our study of 1033 pregnancies, no or post-conception initiation of folic acid supplement use was associated with a 0.8-day delay in embryonic morphologic development. Additionally, an increase of 1 IQR in serum folate (14.4 nmol/L) was associated a 0.4-day advancement in reaching the final Carnegie stage (Stage 23). Serum folate below 25.5 nmol/L was associated with a 1.3-day delay in reaching the final Carnegie Stage. However, smoking, alcohol consumption, caffeine use and physical activity showed no significant association with embryonic development. Inadequate folic acid supplement use is associated with decelerated embryonic development. This emphasises the importance of preconceptional counselling on healthy lifestyle choices to create an optimal environment for the developing embryo.