Intrauterine growth restriction (IUGR) due to placental insufficiency is associated with blood flow redistribution in order to/nmaintain delivery of oxygenated blood to the brain. Given that, in the fetus the aortic isthmus (AoI) is a key arterial/nconnection between the cerebral and placental circulations, quantifying AoI blood flow has been proposed to assess this/nbrain sparing effect in clinical practice. While numerous clinical studies have studied this parameter, fundamental/nunderstanding of its determinant factors and its quantitative relation with other aspects of haemodynamic remodeling has/nbeen limited. Computational models of the cardiovascular circulation have been proposed for exactly this purpose since/nthey allow both for studying the contributions from isolated parameters as well as estimating properties that cannot be/ndirectly assessed from clinical measurements. Therefore, a computational model of the fetal circulation was developed,/nincluding the key elements related to fetal blood redistribution and using measured cardiac outflow profiles to allow/npersonalization. The model was first calibrated using patient-specific Doppler data from a healthy fetus. Next, in order to/nunderstand the contributions of the main parameters determining blood redistribution, AoI and middle cerebral artery/n(MCA) flow changes were studied by variation of cerebral and peripheral-placental resistances. Finally, to study how this/naffects an individual fetus, the model was fitted to three IUGR cases with different degrees of severity. In conclusion, the/nproposed computational model provides a good approximation to assess blood flow changes in the fetal circulation. The/nresults support that while MCA flow is mainly determined by a fall in brain resistance, the AoI is influenced by a balance/nbetween increased peripheral-placental and decreased cerebral resistances. Personalizing the model allows for quantifying/nthe balance between cerebral and peripheral-placental remodeling, thus providing potentially novel information to aid/nclinical follow up.

This study was partially supported by grants from Instituto de Salud Carlos III and Ministerio de Economia y Competitividad (ref. PI11/00051, PI11//n01709, PI12/00801 and SAF2012-37196); Fondo Europeo de Desarrollo Regional de la Unio/ń/nn Europea ‘‘Una manera de hacer Europa’’, Spain; Obra Social ‘La Caixa’,/nSpain; Cerebra Foundation for the Brain Injured Child (Carmarthen, Wales, UK); and the Seventh Framework Programme (FP7/2007-2013) under grant agr/neement/nNo. 611823. PGC was supported by the Programa de Ayudas Predoctorales de Formacio/ń/nn en investigacio/ń/nn en Salud (FI12/00362) from the Instituto Carlos III,/nSpain. MCL wishes to express her gratitude to the Mexican National Council for Science and Technology (CONACyT, Mexico City, Mexico) for supporting h/ner/npredoctoral stay at Hospital Clinic, Barcelona, Spain. The funders had no role in study design, data collection and analysis, decision to publish, or/npreparation of/nthe manuscript