Additive manufacturing (AM) is a disruptive technology for many high-value applications in the biomedical, automotive, and aerospace industries. It has the potential to produce topographically optimized parts consisting of complex geometries previously not possible by traditional subtractive manufacturing methods. However, fatigue properties of powder based selective laser melting components are significantly reduced owing to inherent porosity within them as a consequence of the layer-wise solidification of these components. In order for AM components to be substituted for existing applications, the challenge is to demonstrate enhanced, if not comparable fatigue properties to standard manufacturing approaches. For Al-Si-Mg alloys which are for higher performance, lighter weight, and reduced ecological impact, fatigue is a critical factor. Intrinsic pores amongst other defects act as stress concentrators for fatigue crack initiation during high cycle fatigue. These defects can be caused by entrained gas or hydrogen evolution, as well as lack of fusion. Here in order to better understand their fatigue behavior, the distribution, morphology, size, and shape of these defects have been studied using X-ray CT prior to fatigue testing in order to correlate critical pores observed on the fracture surface, to their original form and location. Further, fatigue properties of a wrought Al-Si-Mg alloy are quantified in the high cycle fatigue regime, alongside additively manufactured AlSi10Mg alloy to quantify and understand the detrimental effect of the defect population.